Class 10 Science

NCERT Solutions For Class 10 Science Chapter 8 How do Organisms Reproduce

Question 1.

1. Name the human male reproductive organ that produces sperm and also secretes a hormone. Write the functions of the secreted hormone.
2. Name the parts of the human female reproductive system where:
   1. Fertilisation takes place.
   2. Implantation of the fertilised egg occurs. Explain how the embryo gets nourishment inside the mother’s body.

Answer:

1. Testes-secrete male hormone-testosterone

Functions:

1. Formation of sperms.
2. Development of secondary sexual characters.

2.

1. Fallopian tube/Oviduct.
2. Uterus.

• The placenta is a special disc-like tissue embedded in the mother’s uterine wall and connected to the foetus/embryo.
• The placenta provides a large surface area for glucose and oxygen/nutrients to pass from the mother’s blood to the embryo/foetus.

How Do Organisms Reproduce NCERT Class 10 Science Solutions

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Question 2. Identify A, B and C in the given diagram and write their functions.

Mention the role of gamete and zygote in sexually reproducing organisms.

Answer:

1. A Stigma, B→ Pollen tube, C→ Female gamete

Functions:

Stigma: It receives pollen.

Pollen tube: It transfers the male gamete.

Female gamete: After fertilization, a zygote is formed which develops into a new individual.

A gamete is a haploid cell which fuses to form a diploid zygote.

After fertilization, the zygote divides several times to form an embryo within the ovule. The ovule develops a tough coat and is gradually converted into a seed.

Question 3. List five distinguishing features between sexual and asexual types of reproduction in tabular form.
Answer:

Question 4. Explain what happens when:

1. Testosterone is released in males.
2. Pollen grain falls on the stigma of the flower.
3. Egg fuses with sperm cells.
4. Planaria is cut into many pieces.
5. Buds are formed on the notches of the Bryophyllum leaf.

Answer:

1. 1. Formation of sperms, change in appearance.
   2. Thick hair grows on the face and the voice begins to crack.
2. A tube grows out of the pollen grain and travels through the style to reach the ovary.
3. Zygote is formed (Fertilization).
4. Each piece grows into a complete organism.
5. Buds may fall on the soil and develop into new plants.

NCERT Class 10 Science Chapter 8: How Do Organisms Reproduce Summary

Question 5. Define the following processes:

1. Fertilization
2. Menstruation
3. Binary fission
4. Vegetative propagation
5. Regeneration

Answer:

1. The fusion of the male gamete with the female gamete is known as fertilization.
2. The cycle which takes place every month when the egg is not fertilized is known as menstruation.
3. It lasts for about two to eight days and during this cycle, the lining of the uterus slowly breaks and comes out through the vagina as blood and mucus.
4. The splitting of the nucleus into two daughter cells which can take place in any plane is known as binary fission. It can be seen in Amoeba.
5. When the vegetative parts of a plant like the root, stem or leaves develop into a new plant under appropriate conditions it is known as vegetative propagation.
6. When the body of an organism cuts into any number of pieces and each piece grows into a complete organism, it is known as regeneration. It can be seen in Hydra and Planaria.

Question 6.

1. Name the parts labelled as A, B, C and D in the diagram given below:
2. What is pollination? State its significance.
3. How does fertilization occur in flowers? Name the parts of the flower that develop into
4. Seed, and
5. Fruit after fertilization.

Answer:

1. Four labelling:
   1. A – Pollen grain
   2. B-Pollen tube
   3. C – Ovary
   4. D-Female germ cell
2. Definition: Transfer of pollen grains from anther to stigma.
   1. Significance: To bring about fertilization.
3. As the pollen lands on the suitable stigma, a pollen tube grows through the style carrying the male germ cell. It reaches the ovary and the male germ cell fuses with the female germ cell and thus fertilization takes place.
   1. Seed → Ovule
   2. Fruit → Ovary

NCERT Solutions Chapter 8: How Do Organisms Reproduce Questions and Answers

Question 7.

1. Draw a sectional view of the human female reproductive system and label the part where:
   1. Eggs develop.
   2. Fertilization takes place.
   3. The fertilized egg gets implanted.
2. Describe, in brief, the changes the uterus undergoes
   1. To receive the zygote.
   2. If a zygote is not formed.

Answer:

1. Diagram:
   1. Labellings: Ovary (Eggs develop)
   2. Fallopian Tube/Oviduct (Fertilization takes place)
   3. Uterus (Fertilized egg gets implanted)
   1. The inner lining of the uterus thickens and is richly supplied with blood.
   2. The inner lining slowly breaks and comes out through the vagina as blood and mucus (menstruation).

Question 8. Write the two causes of the human population explosion. Explain with the help of suitable examples how this explosion can be checked.
Answer:

1. The declining death rates are due to improved medical facilities.
2. Desire for a male child.
3. Less awareness about birth control methods.
4. Illiteracy/poverty (any two)

Population explosion can be checked by:

1. Using contraceptive methods to avoid pregnancy.
   1. Contraceptive methods are used such as
      1. Mechanical barriers
      2. Drugs (as pills)
      3. Loop or copper-T and
      4. Surgical method.
   2. Pills change the hormonal balance and thus prevent the release of egg, hence fertilization is prevented.
2. Spreading awareness about the importance of a small family. This is because an expanding population makes it harder to improve everybody’s standard of living.

NCERT Class 10 Science: How Do Organisms Reproduce Key Concepts

Question 9.

1. Identify the organisms A, and B and the mode of asexual reproduction exhibited by them.
2. How will an organism benefit if it reproduces through spores?
3. Mention the two asexual methods by which Hydra can reproduce. Explain briefly any one such method.

Answer:

1. 1. Bryophyllum-vegetative propagation.
   2. Plasmodium-multiple fission.
2. Spores are covered with thick walls that protect them until they come into contact with a moist surface.
3. Budding and regeneration.

Budding: A bud develops as an outgrowth due to repeated cell division at a specific site, these buds develop into tiny individuals, mature and detach from the parents to become new individuals.

Regeneration: Specialized cells divide to form a large number of cells and undergo changes to become various cell types and tissues.

Question 10. Explain the budding mode of asexual reproduction.
Answer:

Budding: Budding is the forming of offspring from an outgrowth or bud of a parent. The bud may be unicellular or multicellular depending upon the nature of the parent individual.

In coelenterates, tunicates and other multicellular animals it consists of a small number of cells surrounded by an epithelium. Hydra is usually formed in the lower half of the body.

The buds separate from the parent soon after their formation or after some initial growth. In many cases, individuals developed from them do not separate but remain interconnected to form a colony.

NCERT Solutions for Chapter 8: How Do Organisms Reproduce Detailed Explanation

Question 11. Describe the structure of a typical flower.
Answer:

Flower is a modified shoot. It is attached to the stem by a stalk called a pedicel. The swollen tip of the pedicel is called the thalamus.

• On the thalamus are arranged four whorls of floral leaves. The outermost whorl is called calyx which is formed of green leaf-like sepals.
• The second whorl is called corolla which is coloured and formed of petals. The third whorl is called androecium which is formed of stamens. A fourth (innermost) whorl is called gynoecium or pistil and is formed of carpels.
• Stamen has two parts-filament and anther which produces grain-like structures called pollens. Stamen is the male reproductive structure of the plant. The pistil has three parts-basal ovary, long style and stigma at the top. The pistil is the female reproductive structure of the plant.

Question 12. Describe asexual reproduction in Amoeba.
Answer:

Single-celled Amoeba reproduces by the asexual method known as binary fission, i.e., during division, Amoeba splits into two halves. The splitting of the two cells during binary fission can take place in any plane.

During binary fission of amoeba, nuclear division starts first, followed by the constriction in the cell membrane. As the nuclear division completes, constriction deepens and divides into two parts, each containing one nucleus. Finally, two independent daughter amoebae are formed.

Question 13. Why are budding, fragmentation and regeneration all considered asexual types of reproduction? With neat diagrams explain the process of regeneration in Planaria.
Answer:

Budding, fragmentation and regeneration are considered asexual types of reproduction because all of them involve only one parent and gametes are not involved in reproduction. No fertilisation and then zygote formation occur in asexual reproduction.

Class 10 Science Chapter 8: How Do Organisms Reproduce Practice Questions

Question 14. Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.
Answer:

During sexual reproduction, two types of gametes fuse. Although the gametes contain the same number of chromosomes, their DNA is not identical. This situation generates variations among the offspring.

Question 15. Distinguish between pollination and fertilisation. Mention the site and product of fertilisation in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.
Answer:

1. The process or mechanism of transfer of pollen grains from the anther to the stigma is termed pollination.
2. The fusion of male and female gametes giving rise to a zygote is termed fertilisation.
3. The site of fertilisation is ovule.
4. The product of fertilisation is the zygote.

Question 16. Distinguish between a gamete and a zygote. Explain their roles in sexual reproduction.
Answer:

Gamete represents the sex cell or germ cell in sexual reproduction. There are two types of gametes, male and female.

• A zygote is the product of fertilisation in which a male and a female gamete fuse.
• The two fusing gametes possess characters of their parents in their DNA. Fertilisation brings the characters of both parents into one zygote cell.
• The zygote is the first cell of the next generation. It divides to form an embryo which subsequently grows into a new individual.

Question 17. Draw the diagram of a flower and label the four whorls. Write the names of gamete production organs in the flower.
Answer:

1. Male gamete forming part-anther/stamen
2. Female gamete forming part-pistil/ovary/ovule

NCERT Class 10 Science Chapter 8: Reproduction in Organisms

Question 18. What is the placenta? Mention its role during pregnancy.
Answer:

The placenta is a disc-like structure in the lining of the uterine wall. It contains villi on the embryo’s side of the tissues and blood spaces on the mother’s side surrounding the villi. The embryo is connected to the placenta by a tube called the umbilical cord.

Role during pregnancy: It is through the placenta that all the requirements of the developing foetus are met.

The villi provide a large surface area that facilitates the passage of nutrition and oxygen to the embryo from the mother through blood.

Wastes produced by the embryo are removed through the placenta into the mother’s blood.

Question 19. What are various ways to avoid pregnancy? Elaborate on any one method.
Answer:

Ways to avoid pregnancy are called contraceptive methods. They include the following:

1. Mechanical barrier e.g., condom (so that sperm does not reach the egg)
2. Drugs (or pills)-change the hormonal balance so that eggs are not released.
3. Loop or copper-T prevents pregnancy.
4. Surgical method-permanent contraception.

Mechanical barrier: Several methods create a barrier between sperm and egg. Some of them are as follows:

Condoms: It is a fine rubber worn over the penis during sexual intercourse. Semen is collected in it and not discharged into the vagina. This method also prevents the spread of STDs and AIDS.

Diaphragms or caps: They can be fitted in the cervix of a woman to prevent semen from reaching the fallopian tube.

How Do Organisms Reproduce: NCERT Class 10 Science Notes

Question 20. How does fertilisation take place? Fertilisation occurs once a month. Comment.
Answer:

Fertilisation in human beings: The sperm made in the testis of males are introduced into the vagina of the woman through the penis during copulation or mating.

• The sperms are highly active and mobile and thus move up through the cervix into the uterus. From the uterus, sperm pass into the oviducts. The oviduct contains an ovum released by the ovary during ovulation.
• Millions of sperm are released into the vagina at one time, but only one sperm fuses with the ovum in the oviduct to form a zygote. This is called fertilisation.
• Fertilisation can occur only once a month because the ovary releases just one mature egg every month during a menstrual cycle (around the 14th day).

Question 21. Reproduction is essentially a phenomenon that is not for the survival of an individual but for the stability of a species. Justify.
Answer:

All living organisms need energy for their survival and growth. This energy is obtained from various life processes such as nutrition and respiration. Thus, these phenomena are essential for the living of an individual.

• Compared to these life processes, reproduction may appear to be a waste of energy as it is not essential for the survival of an individual. But it is an important function of a living being as it helps in the production of new individuals of its kind. Continuity of life has been possible through reproduction.
• Genetic material is transferred from one generation to the next by DNA copying as a result of reproduction. DNA copying takes place with high constancy and considerable variations.
• This is advantageous for maintaining features that allow the organism to survive in the changing environment. Therefore, reproduction is related to the stability of a species and is not essential for the survival of an individual.

NCERT Solutions for How Do Organisms Reproduce Class 10 Science

Question 22. Describe sexually transmitted diseases and mention the ways to prevent them.
Answer:

Sexually Transmitted Diseases (STDs) are infectious diseases that are transmitted during sexual intercourse. These include bacterial infections such as gonorrhoea and syphilis, and viral infections such as warts and HIV-AIDS. To prevent STDs, the following precautions can be taken:

1. Use a protective covering called a condom, over the penis during sex.
2. Avoid multiple sex partners and maintain personal hygiene.

NCERT Solutions For Class 10 Science Chapter 15 Our Environment Long Question And Answers

Question 1.

1. “Energy flow in a food chain is unidirectional.” Justify this statement. Explain how pesticides enter a food chain and subsequently get into our bodies.
2. What is an ecosystem? List its two main components.

Answer:

1. Because the energy moves progressively through the various trophic levels and is no longer available to the previous trophic level. The energy captured by autotrophs does not revert to the solar input.

• Pesticides, used for crop protection when washed down into the soil/water body, are absorbed by the plant/producer along with water and minerals.
• Being non-biodegradable, these chemicals accumulate progressively in the food chain and enter our bodies.

Our Environment NCERT Class 10 Science Solutions

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2. A self-sustaining functional unit, consisting of living (biotic) and non-living (abiotic) components, is called an ecosystem.

Biotic components: Plants and animals.

Abiotic components: Light, soil, temperature, humidity, wind, air, etc.

Question 2.

1. What is the difference between the food habits of organisms belonging to second and fourth trophic levels? Give one example of organisms belonging to each of these two trophic levels.
2. What are the materials that remain unchanged over long periods?
3. What will happen to the garbage, and dead plants and animals in the absence of decomposers?

Answer:

1. Difference between second trophic level and fourth trophic level:

2. Non-biodegradable material.

3. The natural replenishment of soil will not take place and most of the fertile land will be used by us for dumping waste.

Question 3.

1. State in brief two ways in which non-biodegradable substances would affect the environment. List two methods of safe disposal of the non-biodegradable waste.
2. Differentiate between autotrophs, and heterotrophs and give one example of each

Answer:

The non-biodegradable substances affect the environment in the following ways:

1. They persist in the environment for a long time and thus damage the environment.
2. They cause land and water pollution.

Methods of safe disposal of the non-biodegradable waste:

1. By underground dumping.
2. By sending them to factories for recycling.

Autotrophs: Organisms that can make their food from carbon dioxide and water under the action of sunlight and in the presence of chlorophyll are called autotrophs.

Example: All green plants.

Heterotrophs:

Organisms that cannot make their food by the process of photo synthesis and are dependent on others for food are called heterotrophs.

Example: All animals.

NCERT Class 10 Science Chapter 15: Our Environment Summary

Question 4. Explain the flow of energy between various components ofthe environment.
Answer:

Green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves.

The loss of energy at each step is so great that very little usable energy remains after four trophic levels.

In a food chain, the greatest number of individuals are at the lower trophic level of an ecosystem, and the greatest number is of the producers.

Question 5. Distinguish between biodegradable and non-biodegradable substances. List two effects of each of them on our environment.
Answer:

Effects of biodegradable substances:

1. They release harmful gases like methane, ammonia, carbon dioxide, hydrogen sulfide, etc., during the decomposition process.
2. They release a foul smell only during the decomposition process but they do not cause any type of soil pollution

Effects of non-biodegradable substances:

1. They persist in the environment for a long time and thus, harm the various members of the ecosystem.
2. They release very harmful gases when they are acted upon by physical processes like heat and pressure.
3. They cause pollution of air, soil, and water

NCERT Solutions Chapter 15: Our Environment Questions and Answers

Question 6. How is ozone formed at higher levels of the atmosphere?
Answer:

Ozone is a product of UV radiation on oxygen molecules at higher levels of the
atmosphere. The higher energy radiations split apart some 02 molecules into three oxygen (O) atoms. These atoms then combine with molecular 02 to form ozone.

⇒ \(\mathrm{O}_2+\mathrm{O} \longrightarrow \mathrm{O}_3\)

Question 7. Indicate the flow ofenergy in an ecosystem. Why is it unidirectional? Justify.

1. Usage of-pesticides
2. Manures.

Answer:

The flow of energy generally is as follows:

Sun→ Producer → Herbivore → Carnivore.

Since the flow is progressively from one trophic level to another and does not revert, it is said to be unidirectional. Further, the available energy decreases in the higher trophic levels making it impossible for energy to flow in the reverse direction.

Question 8.

1. What is an ecosystem? List its two main components.
2. We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly Explain.

Answer:

1. A self-sustaining functional unit consisting of living (biotic) and non-living (abiotic) components, is called an ecosystem.

1. Biotic Components: Plants and animals.
2. Abiotic Components: Light, soil, temperature, humidity, wind, air, etc.

2. An aquarium is an artificial and incomplete ecosystem in contrast to a pond or lake which is a natural, self-sustaining, and complete ecosystem. In a natural ecosystem, decomposers help in recycling waste. So, an aquarium needs to be cleaned regularly.

Question 9. Differentiate among autotrophs, heterotrophs, hs, and decomposers andgive one example of each.
Answer:

Autotrophs: Organisms that can make their food from carbon dioxides and water under the action of sunlight and in the presence of chlorophyll are called autotrophs.

Example: All green plants.

Heterotrophs:

Organisms that cannot make their food by the process of photosynthesis and are dependent on others for food are called heterotrophs.

Example: All animals

Decomposers: Organisms that decompose the complex molecules present in the dead remains of plants and animals are called decomposers.

Example: Bacteria, fungi

NCERT Class 10 Science: Our Environment Key Concepts

Question 10. What are trophic levels? Give an example ofa food chain having four steps and name the different levels according to their nutrition habit.

Each step of the food chain is termed the trophic level.

Grass→ Insect → Frog →Snake

Grass – Producer

Insect – Primary consumer

Frog – Secondary consumer

Snake – Tertiary consumer

Question 11. Two things become clear from the energy flow diagram drawn below

Answer:

1. The flow of energy is unidirectional.
2. Only 10%of  energy flows from one trophic level to the next.

Question 12. In the food chain: Grass → Deer→ Lion, operating in a forest, what will happen if all the:

1. Lions are removed?
2. Deer are removed?

Answer:

1. Several deer increases, which will result in less amount of grass, leading to soil erosion.
2. Food available for lions would be less. The amount of grassland will increase.

NCERT Solutions for Chapter 15: Our Environment – Detailed Explanation

Question 13. List two causes of depletion of the ozone layer. Mention any two harmful effects of depletion of this layer.
Answer:

Two causes of the depletion of the ozone layer are:

1. Use of CFCs (chlorofluorocarbon) in refrigeration.
2. Use of CFCs in fire extinguishers and aerosol sprayers.

The harmful effects of the depletion of the  ozone layer are as follows:

Due to the depletion of the ozone layer, UV radiation reaches the earth. This UV radiation causes skin cancer, and damage to the eyes and immune system.

This depletion of the ozone layer may also lead to variations in global rainfall, ecological disturbances, and dwindling global food supplies.

Question 14. Mention the difference between the food habits of organisms belonging to the first and third tropic levels. Give one example of each of them.
Answer:

Class 10 Science Chapter 15: Our Environment Practice Questions

Question 15. Draw a line diagram of a simple food web.
Answer:

Simple food web:

Question 16. What will happen if we kill all the organisms at one trophic level?
Answer:

If we kill all the organisms in one trophic level, the number of organisms in the higher trophic level will decline as they will not get food while the number of organisms in the lower trophic level will increase as they are not eaten up.

For example, if in the following food chain:

Grass → Deer →  Tiger

If we remove all the tigers, the number of deer will increase and the amount of grass will decrease

Question 17.

1. Which scientific term is used for the progressive accumulation of harmful chemicals at each trophic level of a food chain?
2. State any two practices which can help in the protection of our environment.

Answer:

1. Biological magnifications.

2.

1. Use of unpetrol patrol and alternate sources of energy.
2. Disposal of waste after separating into biodegradable and non-biodegradable waste material.

Question 18.

1. Construct the food chain of the forest
2. Construct the food chain of grassland

Answer:

1. Grass → Deer → Tiger

2. Grass→ Grasshopper→ Frog → Snake→ Vulture

Our Environment: NCERT Class 10 Science Explanation and Notes

Question 19. Write the appropriate names ofthe tropic levels Z and X in the figure given below.

Answer:

Z = Tertiary consume

X= Primary consumer.

Question 20. Give any two ways in which non-biodegradable substances would affect the environment.
Answer:

Non-biodegradable substances cannot degrade and return the minerals to the environment. Instead of a cycle, these materials follow a linear path. They are produced in a factory and then end up in the soil. They pile up and cause harm to the various members of the ecosystem.

They may cause biomagnification in the food chain and end upinhumans. For example, pesticides like DDT enter the food chain, biomagnify, and affect human beings and other organisms.

Question 21. What are trophic levels? Give an example ofa food chain and state the different trophic levels in it.
Answer:

The trophic level is the functional level occupied by an organism in a food chain. Trophic means feeding, so trophic levels are the levels or positions at which the species feed. Examples of trophic levels include ‘herbivores’ and ‘decomposers’.

 An example of a food chain depicting various trophic levels is as follows:

Environmental Protection: NCERT Class 10 Chapter 15 Review

Question 22. What is the role of decomposers in the ecosystem?
Answer:

Without decomposers, the remains of the other organisms in a community would accumulate. Eventually, the world would run out of carbon dioxide or nite or phos, phase, or other inorganic materials essential for life. The decomposers break down the organic waste products and dead remains of organisms into the inorganic substances needed by the producers (plants). Most decomposition is carried out by saprophytic fungi and bacteria.

Question 23. What is depicted in the below-mentioned scheme?
Answer: Food Chain 10% law.

NCERT Solutions For Class 10 Science Chapter 16 Management Of Natural Resources Long Question And Answers

Question 1. List two effects of each of them on our environment.
Answer:

Effects of biodegradable substances:

1. They release harmful gases like methane, ammonia, carbon dioxide, hydrogen sulphide, etc., during the decomposition process.
2. They release a foul smell only during the decomposition process but they do not cause any type of soil pollution.

Effects of biodegradable substances:

1. They persist in the environment for a long time and, thus, harm the various members of the ecosystem.
2. They cause pollution of air, soil, and water.

Management of Natural Resources NCERT Class 10 Science Solutions

Question 2. State in brief two ways in which non-biodegradable substances would affect the environment. List two methods of safe disposal of non-biodegradable wastes.
Answer:

The non-biodegradable substances affect the environment in the following ways:

Read and Learn More Class 10 Science Solutions

• They persist in the environment for a long time and thus damage the environment.
• They cause land and water pollution.

Methods of safe disposal of the non-biodegradable waste:

• By underground dumping.
• By sending them to factories for recycling.

Question 3. What are the three problems that crop up due to the building of large dams?
Answer:

The three problems that arise due to the construction of large dams are:

1. Social problem: Displacement of a large number of peasants and tribals.
2. Economic problem: These projects swallow up large amounts of public money without the generation of disproportionate benefits.
3. Environmental problems: They contribute to deforestation and the loss of
   biodiversity.

Class 10 Science Chapter 16: Management of Natural Resources Review

Question 4. How are different stakeholders dependent on forests? Mention any four of them.
Answer:

• Local people living in villages near the forest area.
• Industrialists practicing recycling.
• Wildlife and nature enthusiasts.
• Forest department of the government.

Question 5.

1. Give two reasons why the construction of the Sardar Sarovar Project on the river Narmada and the Tehri Dam on the river Ganga faced opposition.
2. How is mining a cause of pollution?

Answer:

Opposition to these projects was mainly due to two reasons:

1. Social: As they displace large numbers of peasants and tribals without adequate compensation or rehabilitation.

2. Environmental: They contribute enormously to deforestation and the loss of biodiversity.

The extraction of minerals and their processing results in the production of huge amounts of slag, which causes pollution.

NCERT Class 10 Science Chapter 16: Management of Natural Resources Summary

Question 6. Reuse is better than recycling. Give two examples of reuse strategy. Mention any two values we attain from this strategy.
Answer:

Reuse is better than recycling because even in recycling some energy is used while increasing, it is merely to use it again and again without consuming energy,

Example:

• The used envelopes can be reused merely by reversing them.
• The packaging material and thick polythene carry bags can be used many times.
• The plastic bottles of jam or pickles, after being empty, can be used for storing things in the kitchen.
• The mobile phones, cameras, TV sets, a pair of shoes, etc., canbe reused after preparing.
• Values: Environmental concern, awareness, being economically wise, knowledgeable, and justified, making the right decision, etc.

Question 7. Find out about the traditional systems of water harvesting/management in your region.
Answer:

These systems differ from one area to another.

Some traditional systems of water harvesting practiced in India are listed below:

1. Khadins, tanks, and nadis in Rajasthan.
2. Bandharas and tals in Maharashtra.
3. Bundhis in M.P. and U.P.
4. Chars and pyrites in Bihar.
5. Kulhs in Himachal Pradesh.
6. Ponds in the Kandi belt of Jammu region.
7. Eris (tanks) in Tamil Nadu.
8. Surangams in Kerala.
9. Kattas in Karnataka.

Question 8. List five things you have done over the last one week to—

1. Conserve our natural resources.
2. Increase the pressure on our natural resources.

Answer:

1.

1. Planted one tree.
2. Repaired leaking taps.
3. Did not burn coal to heat my room.
4. Reused old envelopes.
5. Did not use motorbikes to go for tuition.

2.

1. Chopped one tree growing in front of my house.
2. Left the lights on while not at home.
3. Burnt coal to heat my room.
4. Left the water tab open.
5. Used motorbikes to go for tuition

Question 9. Following is a list of six traditional water harvesting management systems. Give the names of states of India where they are in practice.

1. Khadins
2. Bundhis
3. Bandharas
4. Eris
5. Kulh
6. Kattas

Answer:

1. Khadins-Rajasthan
2. Bandharas-Maharashtra
3. Kulh-Himachal Pradesh
4. Bundhis-Madhya Pradesh
5. Eris-Tamil Nadu
6. Kattas-Karnataka

NCERT Solutions Chapter 16: Management of Natural Resources Questions and Answers

Question 10.

1. Locate and name the water reservoirs in figure1 and 2
2. Which has an advantage over the other and why?

Answer:

The water reservoir is a pond in Figure (1) and an underground water body in the figure (2)

Figure (2) has more advantages than Figure (1) because the advantages of water stored in the ground are many.

For example

1. It does not evaporate.
2. It spreads out to recharge wells.
3. Provides moisture for vegetation over a wide area.
4. It is protected from contamination by animal and human wastes.
5. It prevents the breeding of insects.

Question 11. In the context of the conservation of natural resources, explain the terms reduce, recycle, and reuse. From among the materials that we use in daily life, identify two materials for each category.
Answer:

Reduce means to use a material/commodity in lesser quantity,

Example: Electricity and water

Recycle means a material that is used once, collected, and sent back to a manufacturer

So that they can make some other useful material from it:

Examples: Plastic cups and buckets, glass tumblers, paper, metal objects

Reuse means using a thing over and over again instead of throwing it away. It does not involve the process of recycling either on a small or large scale: e.g., used envelopes, plastic carry bags, and bottles of jam.

Question 12. Prepare a list of five activities that you perform daily in which natural resources can be conserved or energy utilization can be minimized.
Answer:

1. Unused water in the water bottle may be used for watering plants.
2. Close all the taps before you go to sleep.
3. Avoid using a hose pipe for watering plants.
4. Wash vehicles only when they are dirty.
5. Use a fan and light only when required.
6. Use solar water heating devices.
7. Use CFL in place of conventional bulbs/tubes.

NCERT Class 10 Science: Management of Natural Resources Key Concepts

Question 14. Is water conservation necessary? Give reasons.
Answer:

Conservation of water is necessary due to the following reasons:

• Uneven distribution—some parts of our country have high resources of water whereas other parts suffer from chronic water shortage.
• Wide seasonal as well as yearly fluctuation in rainfalls.
• Water in rivers and ponds is polluted by dumping of untreated sewage and industrial wastes into it.
• The changing lifestyle of people, especially in urban areas, is consuming more water.

Question 15. Suggest a few useful ways of utilizing wastewater.
Answer:

Wastewater can be used for the following:

• Recharging the groundwater
• Can be used for irrigation
• Treated municipal water can be used for washing cars, watering the gardens
• Certain pollutants in sewage water can become fertilizer for various crops.

NCERT Solutions for Chapter 16: Management of Natural Resources – Detailed Explanation

Question 16. What is the importance of forests as a resource?
Answer:

Forests are renewable resources that provide:

• Habitat, food, and protection of wildlife.
• Help in balancing CO₂ and O₂ of the atmosphere.
• Improve the water-holding capacity of soil.
• Regulate the water cycle.
• For human beings, they are the source for all essential commodities like fuel, wood, timber, pulp and paper, etc.
• Useful products like fruits, resins, gums, essential oils, hide wrappers, etc.

NCERT Solutions For Class 10 Science Chapter 5 Periodic Classification Of Elements

Question 1. Why did Mendeleev have gaps in his periodic table?

1. State any three limitations of Mendeleev’s classification.
2. How does the electronic configuration of atoms change in a period with an increasein atomic number?

Answer:

1. Gaps were left for undiscovered elements in the periodic table.

2.

1. The position of hydrogen was not justified.
2. Increasing order of atomic mass could not be maintained.
3. Isotopes cannot be given in separate places.

Several shells remain the same number of valence electrons, increasing from left to right in a period till the octet is complete.

Periodic Classification of Elements NCERT Class 10 Science Solutions

Question 2. An element X which is a yellow solid at room temperature shows catenation and allotropy. ‘X’ forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystal and are the major air pollutants.

1. Identify ‘X.
2. Write its electronic configuration.
3. Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals.
4. What would be the nature (acidic/basic) of oxides formed?
5. Locate the position of the element in the periodic table.

Read and Learn More Class 10 Science Solutions

Answer:

1. X’ is sulphur.

2. Electronic configuration of ‘X’ is 2, 8, 6.

SO₂ and SO₃ are acidic oxides.

It belongs to Group 16 and 3rd period.

Question 3. An element placed in the 2nd group and 3rd period of the periodic table burns in presence of oxygen to form a basic oxide.

1. Identify the element.
2. Write its electronic configuration.
3. Write the balanced equation when it burns in the presence ofair.
4. Write a balanced equation when this oxide is dissolved in water.
5. Draw the electron dot structure for the formation ofthis oxide.

Answer:

1. Magnesium

2. Electronic configuration- 2, 8, 2

3. 2 Mg+O₂ → 2MgO

4. MgO+H₂O→ Mg (OH)₂

5.

⇒ \( \underset{2,8,2}{\mathrm{Mg}} \longrightarrow \underset{2,8}{\mathrm{Mg}^{2+}}+2 e^{-} \)

⇒ \( \underset{2,6}{\mathrm{O}}+2 \mathrm{c}^{-} \longrightarrow \underset{2,8}{\mathrm{O}^{2-}}\)

Question 4. An element X (Atomic number 17) reacts with an element Y (atomic number 20) to form a divalent halide.

1. Where in the periodic table are elements X and Y placed?
2. Classify X and Y as metal (s) and non-metals or metalloids.
3. What will be the nature of the oxide of element Y? Identify the nature of bonding in the compound formed.
4. Draw the electron dot structure ofthe divalent halide.

Answer:

1. ‘X’ is in group 17 and 3rd period. ‘Y’ is in group 2 and 4th period.
2. X is non-metal, V is metal.
3. X forms basic oxide. It has ionic bonding in the compound formed.

Question 5. Two elements ‘P’ and ‘Q’ belong to the same period ofthe modernperiodic table and are in Group-1 and Group-2 respectively. Compare their following characteristics in tabular form:

1. The number ofelectrons in their atoms.
2. The sizes oftheir atoms
3. Their metallic characters
4. Their tendency to lose electrons
5. The formula oftheir oxides
6. The formula oftheir chlorides

Answer:

Question 6.

1. Why do we classify elements?
2. What were the two criteria used by Mendeleev in creating his Periodic Table?
3. Why did Mendeleev leave some gaps in his Periodic Table?
4. In Mendeleev’s Periodic Table, why was there no mention ofNoble gases like Helium, Neon and Argon?
5. Wouldyou place the two isotopes of chlorine, Cl-35 and Cl-37in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.

Answer:

1. Classification of elements helps in:

1. Systematic study of the properties of elements.
2. I am understanding and remembering the properties of elements.

2. The two criteria used by Mendeleev were:

1. Increasing order of atomic mass.
2. Similarity in the properties ofthe elements.

3. Mendeleev left a gap in his periodic table for the undiscovered elements like germanium, and gallium.

4. There was no mention of noble gases like helium, neon and argon as they were notknown at that time, and were discovered much later.

5. According to Mendeleev’s periodic table Cl-35 and Cl-37 should be placed at different positions as the basis of classification is increasing order of atomic masses but since their chemical properties are the same they should be placed in the same position in the periodic table.

NCERT Class 10 Science Chapter 5: Periodic Classification of Elements Summary

Question 7. The atomic radii ofthe element of second period are given below:

1. Arrange these elements in decreasing order oftheir atomic radii.
2. Are the elements now arranged in the pattern ofa period in the periodic table?
3. Name the element which has the (a) largest and (b) smallest atomic number.
4. From the above data, infer how the atomic size or atomic radius ofthe elements changes as we go from left to right in a period.
5. Name one metal, one non-metal and a metalloid out of these elements.
6. Why does atomic radius decrease as we move from left to right in a period?

Answer:

1.

2. Yes, the elements are now arranged in the pattern ofa period of the periodic table.

3.

1. Li has the smallest atomic number.
2. F has the largest atomic number.

4. Atomic radius decreases on moving from left to right in a period ofthe periodic table

5. Metal: Li, non-metal: C, Metalloid: B

6. Force of attraction for the outermost electrons increases because of increased nuclear charge.

Question 8. 

Consider the table given above and answer the following questions:

1. Name the most reactive metal.
2. How many shells does ‘d’ have?
3. Name the element(s) having valency 2.
4. How many valence electrons does j’ have?
5. Which is more non-metallic, ‘Id or ‘V?
6. The atom of which element is bigger, ‘e’ or ‘h’?

Answer:

1. d
2. 4
3. e/g
4. 2
5. h
6. e

Question 9. Given below are some elements ofthe modern periodic table: ₄Be, ₉F, ₁₄Si, ₁₉K, ₂₀Ca

1. Select the element that has one electron in the outermost shell and write its electronic configuration.
2. Select two elements that belong to the same group. Give a reason for your answer.
3. Select two elements that belong to the same period. Which one of the two has a bigger atomic size?

Answer:

₁₉K, its electronic configuration is: 2, 8, 8, 1

₄Be, ₂₀Ca (Both have two valence electrons and in a group valence electrons remain the same).

₄Be, ₉F belongs to the same period. The atomic size ofBe is bigger because in a period, atomic size decreases due to increased nuclear charge.

Question 10. Study the following table in which the positions of six elements A, B, C, D, E and F are shown as they are in the modern periodic table:

Periodic Classification of Elements: NCERT Class 10 Science Key Concepts

Based on the above table, answer the following questions:

1. Name the element which forms only covalent compounds.
2. Name the element which is a metal with valency three.
3. Name the element which is a non-metal with valency three.
4. Out ofD and E, which is bigger and why?
5. Write the common name for the family to which the elements C and F belong.

Answer:

1. E
2. D
3. B
4. D is bigger; atomic radius/size decreases from left to right along a period.
5. Noble gases

Question 11. The atomic number ofan element is 17. Predict (a) its valency, (b) whether it is a metalor non-metal, and (c) its relative size concerning other members of its group. Justify your answer in each case. (CBSE 2011, 2013)
Answer:

1. 1(-1).It has electronic configuration = 2, 8, 7. Therefore, it requires one more electron to become stable.

2. Non-metal. Because it will show the tendency to gain electrons.

3. It belongs to the third period and it has a smaller size as compared to other members of this period because the size of the atom decreases in a period due to an increase in the nuclear charge.

Note: It belongs to group 17, which is of non-metals and in this group, it is bigger than fluorine but smaller than another member.

Question 12. Atomic radii of the elements of the second period are given below:

1. Arrange them in decreasing order oftheir atomic radii.
2. Are the elements now arranged in the pattern of a period in the Periodic Table?
3. Which elements have the largest and the smallest atoms?
4. How does the atomic radius change as you go from left to right in a period?

Answer:

The elements of the second period in the decreasing order of their atomic radii are:

1.

2. Yes, the above elements are arranged in the pattern of a period in the periodic table.

3. Li has the largest (152 pm) and O has the smallest (66 pm) atoms.

4. The atomic radii decrease as we move from left to right in a period due to a corresponding increase in their nuclear charge.

Question 13. Give reasons for the following:

1. Lithium atoms are smaller than sodiuatomsom.
2. Chlorine (Atomic Number 17) is more electronegative than Sulphur (Atomic Number

Answer:

1 The electronicic configuration of Li is 2,1 and that of Na is 2, 8, 1. Since sodium has more shellit hashus a larger size.

2. E.C. of Cl = 2, 8,7

E.C. of S = 2, 8,6.

As sulphur is placed before chlorine in the periodic table, soit has a bigger size andits tendency to gain electrons is lesser than Cl.

Question 14. Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements: K, C, Al, Si, and Ba.
Answer:

1. The element K (potassium) is in groups of Mendeldev’s Periodic Table in which the general formula of the oxides of elements is R₂ O.

• So, the formula of an oxide of K will be K₂O.

2. The element C (carbon) is in group IV of Mendeleev’s periodic table in which the general formula of the oxides of elements is RO₂.

• So, the formula of an oxide of C will be CO₂

3. The element Al (aluminium) is in group 3 of Mendeleev’s periodic table in which the general formula of the oxides of elements is R₂O₃.

• So, the formula of the oxide of Al will be Al₂O₃.

4 The element Si (Silicon) is in group IV of Mendeleev’s periodic table in which the general formula for the oxides of elements is RO₂.

• So, the formula of the oxide of Si will be SiO_2.

5. The element Ba (Barium) is in group II of Mendeleev’s periodic table in which the general formula for the oxides of elements is RO.

• So, the formula of the oxide of Ba will be BaO.

NCERT Solutions Chapter 5: Periodic Classification of Elements Questions and Answers

Question 15. An atom has electronic configurations 2, 8, and 7.

1. What is the atomic number of this element?
2. To which of the following elements would it be chemically similar?

(Atomic numbers are given in parentheses.) N(7) F(9) P(15) Ar(18)

Answer:

The atomic number (equal to number of electrons in a neutral atom) of the element would be 2 + 8 + 7 = 17.

Examine the electronic configuration of the given elements:

N(7) – 2,5

F(9) – 2,7

P(15) – 2,8,5

Ar(18) – 2,8,8

The electronic configuration of F(9) is similar to that of the given element (2, 8,

Therefore, F is chemically similar to the given element.

Question 16. The position of three elements A, B, and C in the Periodic Table are shown below

1. State whether A is a metal or non-metal.
2. State whether C is more reactive or less reactive than A.
3. Will C be larger or smaller in size than B?
4. Which type of ion, cation or anion, will be formed by element A?

Answer:

1. A is a non-metal.
2. C is less reactive than A.
3. C will be smaller in size than B.
4. A will form an anion.

Question 17. In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
Answer:

The electronic configuration of elements:

1. Atomic number 12: 2, 8, 2

2. Atomic number 19: 2, 8, 8, 1

3. Atomic number 20: 2, 8, 8, 2

4. Atomic number 21: 2, 8, 8, 3

5. Atomic number 38: 2, 8, 18, 8, 2

6. Element with atomic number 12 will have similar physical and chemical properties as element 38 as both have two electrons in the outermost shell.

Question 18. Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
Answer:

Question 19. Three elements ‘X’, and ‘Z’having atomic numbers 11,7 and 6 respectively react with oxygen to form their oxides.

1. Arrange these oxides in increasing order oftheir basic nature.
2. Give a reason for your answer.

Answer: ₁₁X = 2, 8, 1

₇Y = 2, 5

₆Z = 2, 4

160 Scionco-X

1. Y < Z < X

2. X is metallic hence, its oxide is basic. While Y and Z are non-metals and their oxides are acidic.

(In a period, acidic character and basic character decrease).

NCERT Class 10 Science: Periodic Classification of Elements Explanation and Notes

Question 20. An element belongs to the third period and second group ofthe periodic table:

1.  State the number of valence electrons in it.
2. Is it a metal or a non-metal?
3. Name the element.
4. Write the formula of its oxide.

Answer:

1. 2 valence electrons
2.  Metal
3. The element is Magnesium.
4. Magnesium oxide, MgO.

Question 21. The atomic number of K and Ca is 19 and 20 respectively and they belong to the same period.

1. Which of them would have a smaller atomic size?
2. Which one would be more electropositive?
3. To which group would each of them belong?

Answer:

1. Ca, as size decreases in a period due to an increase in the effective nuclear charge.
2. K, as electropositive character decreases in a period due to an increase in the effective nuclear charge.
3. K belongs to group 1 (Alkali Metals). Ca belongs to group 2 (Alkaline Earth Metals).

Question 22. Justify the following statements:

1. Cations are smaller in size than the corresponding atom.
2. The size ofthe atom increases as we move down a group.
3. Atomic size decreases as we move across a period.

Answer:

1. Because cations are formed bythe loss of valence electrons. This decreases the nuclear
2. charge and thus size of cations decreases.
3. Because new shells are being added as we go down the group.
4. It is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.

Question 23. The formula of magnesium oxide is MgO. State the formula of barium nitrate and barium sulphate, if barium belongs to the same group as magnesium.
Answer:

Answer:

Question 24. Apart TPeriodicdic Table has been shown below:

Answer the following questions based on the position of elements in the above table.

1. Which element is a noble gas? Give reason.
2. Which element is most electronegative? Give

Write the electronic configuration of(a) B and (b) E.

Answer:

1. G – It is a noble gas and has zero valency.

2. E- Smallest atomic size and more electron affinity.

3.

1. 2, 8, 1
2. 2,7

Question 25.

1. State Modern Periodic Law.

2. How many

1. Groups and
2. Periods are present in the modern periodic table?

Periodic Table and Classification of Elements NCERT Solutions

Question 26. State how the problem of placing:

1. Hydrogen
2. Isotopes ofan element have been solved in this periodic table.

Answer:

1. The properties of elements are the periodic function of their atomic numbers.

2.

1. 18 groups
2. 7 periods

3.

1. Hydrogen in 1st group.
2. Isotopes ofan element at one place.

Question 27. Given below are four elements with their atomic numbers

1. Identify the elements which belong to the same group ofthe Modern Periodic Table.
2. Arrange the given elements in decreasing order of atomic size.
3. Write the formula ofthe oxides of B.
4. Which ofthe above elements is a metalloid?

Answer:

1. B and C
2. B > D > A > C
3. B₂O
4. D

Question 28. The following table shows elements represented by the letters A, B, C, D, E, F, G and H.

1. Which ofthe elements has the atomic size:

1. Biggest
2. Smallest

2. Which element has valency:

1. 3
2. Zero

Answer:

1.

1. A
2. G

2.

1. C
2. H

Question 29. Three elements A, B and C have atominumberser 7, 8 and 9 respectively.  What would be their positions in the modern periodic table? (Mention group and period both).

1. Arrange A, B and C in the decreasing order oftheir size.
2. Which one ofthe three elements is most reactive and why?

Answer:

1.

Position of A = 15th group, 2nd period

Position of R = 16th group, 2nd period

Position of C = 17th group, 2nd period

2. A > B > C

3. C is the most reactive as it has the smallest size, so it can easily gain electrons.

Question 30.

1. The elements ofthe second period along with their atomic number in parentheses are given below: B (5), Be (4), O (8), N (7), i (3), C (6), F (9)

1. Arrange them in the same order as they are in the periodic table.
2. Which element has the largest and smallest atom?

2. Why does the atomic radius change as we move from left to right in a period?

Answer:

1.

1. Li, Be, B, C, N, O, F
2. The largest atom is Lithium and the smallest is Fluorine.

2. The atomic radius decreases in moving from left to right along a period.

This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.

Question 31. An element X(atomic number 7) reacts with an element Y(atomic number 20) to form a divalent halide.

1. Where in the periodic table are elements X and Y placed?
2. Classify X and Y as metal(s), non-metal(s) or metalloid(s).
3. What will be the nature of the oxide of element Y? Identify the nature of bonding in the compound formed.
4. Draw the electron dot structure ofthe divalent halide.

Answer:

1. X belongs to group 17 and 3rd period

Y belongs to group 2 and 4th period

2. X-non metal

Y-metal

3. Basic oxide; Ionic bonding

Question 32. Atomic number ofa few elements is given below 10,20,7,14

1. Identify the elements.
2. Identify the Group number of these elements in the PeriodicIable.
3. Identify the Periods of these elements in the PeriodicIable.
4. What would be the electronic configuration for each of these elements
5. Determine the valency of these elements.

Answer:

1. Elements—Neon (Ne), Calcium (Cu), Nitrogen (N), Silicon (Si)

2. Group— 18, 2, 15, 14

3. Period— 2,4,2,3

4. Electron configuration

₁₀Ne = 2, 8

₂₀Ca = 2, 8, 8, 2

₇N = 2, 5

₁₄Si = 2, 8, 4

Valency— Ne(O), Ca(2), N(3), Si(4)

Class 10 Science Chapter 5: Periodic Classification of Elements Practice Questions

Question 33. Complete the following crossword puzzle

Across:

1. An element with atomic number 12.

3. Metal used in making cans and member ofGroup 14.

4. A lustrous non-metal which has 7 electrons in its outermost shell.

Down:

2. Highly reactive and soft metal which imparts a yellow colour when subjected to flame and is kept in kerosene.

5. The first element of the second Period.

6. An element which is used in making fluorescent bulbs and is the second member of Group18 in the Modern Periodic Table.

7. A is a radioactive element which is the last member of the halogen family.

8. Metal which is an important constituent of steel forms rust when exposed to moist air.

9. The first metalloid in the Modern Periodic Table whose fibres are used in making bulletproof vests.

Question 34. 

1. In this ladder symbols of elements jumbled up. Rearrange these symbols of elements in the increasing order oftheir atomic number in the Periodic Table.
2. Arrange them in the order of their group also.

Answer:

1. H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca

2.

Group 1 — H, Li, Na, K

Group 2 — Be, Mg, Ca

Group 13 — B, Al

Group 14—C, Si

Group 15—N, P

Group 16—O, S

Group 17—F, Cl

Group 18 —He, Ne, Ar

Question 35. Mendeleev predicted the existence of certain elements not known at the time and named two of them as Eka-silicon and Eka-aluminium.

1. Name the elements which have taken the place of these elements.
2. Mention the group and the period of these elements in the Modern Periodic Table.
3. Classify these elements as metals, non-metals or metalloids.
4. How many valence electrons are present in each one of them?

Answer:

Germanium (Ge) and Gallium (ga)

Group 14; Period 4 and Group 13; Period 4

Ge-Metalloid; Ga-Metal

Ga-3, Ge-4

Question 36.

1. The electropositive nature ofthe element(s) increases down the group and decreases across the period.
2. The electronegativity of the element decreases down the group and increases across the period.
3. Atomic size increases down the group and decreases across a period (left to right).
4. Metallic character increases down the group and decreases across a period. On the basis ofthe above trends ofthe Periodic Table, answer the following about the elements with atomic numbers 3 to 9.
   1. Name the most electropositive element among them.
   2. Name the most electronegative element.
   3. Name the element with the smallest atomic size.
   4. Name the element which is a metalloid.
   5. Name the element which shows maximum valency.

Answer:

1. Lithium
2. Fluorine
3. Fluorine
4. Boron
5. Carbon

Question 37. An elementX which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition offer sulphate crystals and are the major airpollutants.

1. Identify the element X.
2. Write the electronic configuration of X.
3. Write the balanced chemical equation for the thermal decomposition of ferrous sulphate.
4. What would be the nature (acidic/ basic) of oxides formed?
5. Locate the position ofthe element in the Modern Periodic Table.

Answer:

1. Element X is sulphur (atomic Number 16)

2. K-2, L- 8-6 M

3.

4. Acidic

5. 3rd period, group 16

NCERT Solutions for Periodic Classification of Elements Class 10

Question 38. An element X of group 15 exists as a diatomic molecule and combines with hydrogen at 773K in the presence ofthe catalyst to form a compound ammonia which has a characteristic pungent smell.

1. Identify the element X. How many valence electrons does it have?
2. Draw the electron dot structure of the diatomic molecule of X. What type of bond is formed in it?
3. Draw the electron dot structure for ammonia and what type of bond is formed in it.

Answer:

1. Nitrogen (atomic number 7)

2,5; it has 5 valence electrons

2.

3.

Question 39. Which group of elements could replaced in Mendeleev’sPeriodic Table without disturbing the original order? Give reason.
Answer:

Noble gases

According to Mendeleev’s classification, the properties of elements are the periodic function of their atomic masses and there is a periodic recurrence of elements with similar physical and chemical properties. Noble gas being inert, could be placed in a separate group without disturbing the original order.

Question 40. Give an account of the process adopted by Mendeleev for the classification of elements. How did he arrive at “Periodic Law”?
Answer:

• 63 elements were known.
• Compounds of these elements with oxygen and hydrogen were studied (formation of oxides and hydrides)
• Elements with similar properties were arranged in a group
• Mendeleev observed that elements were automatically arranged in the order of increasing atomic masses.

Question 41. The properties of the elements are given below. Where would you locate the following elements in the periodic table?

1. A soft metal stored under kerosene.
2. An element with variable (more than one) valency stored under water.
3. An element which is tetravalent and forms the basis of organic chemistry.
4. An element which is an inert gas with atomic number 2.
5. An element whose thin oxide layer is used to make other elements corrosion-resistant by the process of”anodising”.

Answer:

1. Sodium (Na) Group 1 and Period 3 or Potassium (K) Group 1 and Period 4
2. Phosphorus (P) Group 15 and Period 3
3. Carbon (C) Group 14 and Period 2
4. Helium (He) Group 18 and Period 1
5. Aluminium (Al) Group 13 and Period 3

Question 42. Given below are the meltingpoints and atomic radii of three elements X, Y, and Z of the periodic table having V electrons in the outermost shells of their atoms:
Answer:

Question 43. What similarity was observed by Newlands in the properties of elements arranged in the increasing order of their atomic masses and the octaves of music? How many elements were known at the time of Newlands?
Answer:

Newlands observed that as in music eighth note is repeated in an octave of music, when the elements are arranged in the order of increasing atomic masses, the properties of the eighth element (starting from a given element) are a repetition of the properties of the first element.

From the above table, it is observed that sodium at serial number 8 has similar properties to the first element, lithium. There were only 56 elements known at the time of Newlands.

NCERT Solutions for Periodic Classification of Elements Class 10

Question 44. Three elements A, B, and C have atomic numbers 7, 8, and 9 respectively.

1. What would be their positions in the Modern Periodic Table (Mention group and period both)?
2. Arrange A, B, and C in the decreasing order oftheir size.
3. Which one ofthe three elements is most reactive and why?

Answer:

1.

Element A- group (5A or 15), period 2

Element B- group (6A or 16), period 2

Element C- group (7A or 17), period 2

2. A > B > C

3. C is the most reactive. It can easily attract one electron to acquire a stable electronic configuration of Ne.

Question 45. What is a group in a periodic table? In what part ofgroup would you separately expect the elements to have

1. The greatest metallic character
2. The largest atomic size

Answer:

The group is a vertical column in the periodic table. The elements placed in a vertical column in the periodic table are said to belong to the same group.

As the metallic character increases on going down a group, the greatest metallic character is expected to be shown by the elements in the lowest part of a group.

Atomic size increases on moving down a group. So element at the bottom of a group would be of the largest size in that group.

Question 46. Barium is an element of atomic number 56. Look up its position in the periodic table and answer the following?

1. Is it a metal or a non-metal?
2. Is it more reactive than calcium or less?
3. What will be its valency?
4. What will be the formula of barium chloride?
5. Will it be larger than its neighbour (caesium) or smaller?

Answer:

1. It is a metal as it is placed under calcium and strontium.
2. It is more reactive than calcium because in this case outermost shell is farther away from the nucleus and it can more easily lose electrons.
3. Valency is 2 as it belongs to group 2.
4. BaCl₂

It is smaller in size than its neighbour Caesium as it is next to Caesium iththe e n 6th period of the periodic table. Atomic size decreases as we move from left to right in a period.

Question 47. Properties of some elements are given below. Identify in each case the element and group in the periodic table to which it belongs.

1. A soft metal stored under kerosene.
2. An element with variable valency stored under water.
3. An element which is tetravalent and forms the basis of organic chemistry.
4. An element which is an inert gas with atomic number 2.
5. A metal which burns with brilliant light when ignited.
6. An element which is yellow solid at room temperature that shows catenation and allotropy.

Answer:

Question 48. Dobereiner arranged the elements in the order of increasing atomic masses in a triad. The arrangement was modified by Newlands and later by Mendeleev. Even Mendeleev’s arrangement was later modified by Mosley resulting in the modern periodic table.

There are many other similar examples in the history ofscientific advancement where theories and, novels were modified by later scientists and original contributions accepted these modifications happily.

Answer the following based on the above data:

1. How does Modern periodic law differ from periodic law given by Mendeleev?
2. What scientific values can be associated with the above anecdotes?
3. Give an example from your life experiences so far that reflects the display of such values by you.

Answer:

1. Mendeleev’s periodic law states that the properties of elements are the periodic function of their atomic masses. Mosley’s modern periodic law states that the properties of elements are a periodic function of their atomic number.
2. Open-mindedness, ability to accept failure, intellectual honesty, respect for other’s views, spirit of enquiry.
3. Acceptance of wrong traditional beliefs initially and change in these beliefs at a later stage.

Question 49. Ria and Rama are students of Class-10 Ria is very much organised and maintained. The teachers love her. She earns great respect in the class whereas Rama is unorganised and always faces a lot of problems in handling life situations. Answer the following questions based on the above information:

1. In your opinion how does organisation help in daily life?
2. How can you relate the above fact with the Chapter classification of elements?
3. How does the classification of elements help us in studying them properly?

Answer:

The organisation makes our life simple, easy and systematic

As classification and organisation help in our daily life in the same way classification of elements has made the study of elements easier and simple.

We can know about the properties of elements because of this ‘classification.

Periodic Classification of Elements: Trends and Properties NCERT

Question 50. Given below are three groups ofthree elements each with their respective atomic masses. Can you find which of these groups form the Dobereiner triad?

Answer:

Only group B forms Dobereiner triad

⇒ \(\left(\mathrm{Sr}=87.6 \frac{40.1+137.3}{2}=\frac{1774}{2}=88.7\right)\)

Question 51. Elements A, B, C, D, E, F, G, H, I, and J have atomic weights as 3, 7, 9, 13, 35, 19, 25, 30, 50, and 97 respectively. Which are the two elements having similar properties according to Newlands’ law of octaves? What are their atomic weights? Explain.
Answer:

According to Newlands’ law of octaves, if the elements are arranged in the increasing order of their atomic weights, then the first and eighth elements have similar properties.

Thus, we have:

The first and eighth elements are A and E—which have similar properties. Their atomic weights are 3 and 35 respectively. Similarly, elements B, I and C, J are other pairs.

NCERT Solutions For Class 10 Science Chapter 3 Metals And Non-Metals Long Question And Answers

Question 1. Explain the process by which the metal is obtained from its molten chloride.
Answer:

Sodium

4Na + O₂ → 2Na₂O

Na₂O+ H₂O → 2NaOH

Sodium is obtained from sodium chloride by the process of electrolytic reduction.

Reactions: At cathode: Na+ + e → Na

At anode: 2Cl^–→ Cl₂ + 2e ̄

Metals and Non-Metals NCERT Class 10 Science Solutions

Read and Learn More Class 10 Science Solutions

Question 2.

In the formation of a compound between two atoms A and B, A loses two electrons and B gains one electron. What is the nature of the bond between A and B?

1. Suggest the formula of the compound formed between A and B.
2. On similar lines explain the formation of the MgCl₂, molecule.
3. Common salt conducts electricity only in the molten state. Why?
4. Why is the melting point of NaCl high?

Answer:

1.

1. Ionic Bond

2.

2. Mg → Mg⁺  + 2e^–

2Cl + 2e → 2CH^–

3. Na⁺ and Cl^– are free to move in the molten state but not in a solid state.

4. It is due to the strong force of attraction between Na⁺ and Cl^–.

Question 3. Seema cooks and sometimes overcooks food to make it tender irrespective of the fact that it destroys some nutrients. She adds spices, sugar and/or salt to make it tastier and enjoyable.

Geeta uses plant roots and fruits which have enough sugar. She uses food of a vegetable origin which is better than animal origin. Seema enjoys spicy food but also takes one tablet for heartburn, one for digestion and another to release constipation.

She uses stale food or the food repeatedly warmed which loses its nutritive value. She uses frozen and preserved food which has a shelf life, after which it is inedible.

1. Why should we prefer food from vegetable origin and not from animal origin?
2. Why should we not take spicy food?
3. Why should we not overcook food?
4. Why should we not take frozen and preserved food and always prefer fresh food?
5. What values are possessed by Geeta?

Answer:

1. Food of vegetable origin is less complex and easily digestible as compared to food of animal origin.

2. It leads to indigestion and sometimes constipation and heartburn.

3. It will lead to loss of nutrients.

4. It has a shelf life and is not fit for use and after sometimes it becomes stale. Fresh food is rich in nutrients.

5. Geeta has good eating habits and she keeps her family healthy.

Question 4.

1. An ore on treatment with dilute hydrochloric acid produces brisk effervescence. What step will be required to obtain metal from the enriched ore?
2. Copper coin is kept immersed in silver nitrate solution for some time. What change will take place in the coin and the colour of the solution? Write a balanced chemical equation of the reaction involved.

Answer:

1. Carbonate ore

Steps

1. Calcination: Carbonate ore is heated in a limited supply of air and oxide is obtained,

Example: 

ZnCO(s) → (Heat) → ZnO(s) +CO(g)

Reduction with carbon: Oxide ore is heated with carbon

ZnO(s) + C(s) → Zn(s) + CO(g)

2. Copper, being more reactive than silver will displace silver from the silver nitrate solution and there will be deposition of silver on a copper coin. The colour of the solution will turn to blue.

Example:

Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)

NCERT Class 10 Science Chapter 3: Metals and Non-Metals Summary

Question 5.

1. List two differences between calcination and roasting in tabular form.

2. Which method will you use to reduce the following? Explain by giving a suitable example.

1. Oxides of less reactive metals.
2. Oxides of moderately reactive metals.
3. Oxides of highly reactive metals.

Answer:

1. 

2.

1. Self-reduction (In the presence of heat).

2HgO → (Heat) → 2Hg+O

2Cu₂O+Cu₂S  →  (Heat) →  6Cu +SO₂

2.  Reduction using carbon.

ZnO + C→ Zn + CO

Sometimes, some highly reactive metals are used as reducing agents.

Example:

3MnO₂ + 4Al→ 3Mn + 2Al₂O₃ + Heat

Or Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + Heat

3. Electrolytic reduction.

Example: Na, Mg, and Ca are obtained by electrolysis of their molten chlorides.

Question 6. Write a chemical equation when zinc granules react with:

1. Sulphuric acid
2. Hydrochloric acid
3. Aluminium chloride
4. Sodium hydroxide

⇒ \(\mathrm{Zn}+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{ZnSO}_4+\mathrm{H}_2\)

⇒  \(\mathrm{Zn}+2 \mathrm{HCl} \longrightarrow \mathrm{ZnCl}_2+\mathrm{H}_2\)

⇒  \(\mathrm{Zn}+\mathrm{AlCl}_3 \longrightarrow \text { No reaction }\)

⇒  \(\mathrm{Zn}+2 \mathrm{NaOH} \longrightarrow \mathrm{Na}_2 \mathrm{ZnO}_2+\mathrm{H}_2\)

⇒  \(\mathrm{Zn}+4 \mathrm{HNO}_3 \longrightarrow \mathrm{Zn}\left(\mathrm{NO}_3\right)_2+2 \mathrm{NO}_2+2 \mathrm{H}_2 \mathrm{O}\)

Question 7. State reason why

1. Ionic compounds have high melting and boiling points.
2. Ionic compounds are soluble in water.
3. Ionic compounds are solid and somewhat hard.
4. Ionic compounds conduct electricity in a molten state.
5. The metals tend to lose electrons.

Answer:

1. Ionic compounds have high melting and boiling points because a considerable amount of energy is required to break the strong inter-ionic attraction.
2. Ionic compounds are soluble in water because their oppositely charged ions break by the opposite pole of water molecules.
3. They are solids and are somewhat hard because of the strong force of attraction between the positive and the negative ions.
4. Ionic compounds conduct electricity in a molten state because the electrostatic forces of attraction between the oppositely charged ions are overcome due to heat.
5. Metals lose electrons as a tendency to attain a filled valence shell.

Question 8. Here are some general statements. Give one exception for each statement.

1. Metals are lustrous.
2. Metals are solids at room temperature.
3. Metals have a high melting point.
4. Non-metals are non-lustrous.
5. Non-metals are insulators or non-conductors of electricity.

Answer:

1. Sodium
2. Mercury
3. Gallium
4. Iodine
5. Carbon

NCERT Solutions Chapter 3: Metals and Non-Metals Questions and Answers

Question 9.

1. Write two differences between calcination and roasting.

2. No reaction occurs when granules of solid ‘A’ are mixed with a powder of solid ‘B’: However when the mixture is heated, a reaction starts with the evolution of much heat.

Product ‘C’ of the reaction settles down as a liquid metal and solid product ‘D’ keeps floating over the liquid ‘C’. This reaction is sometimes used to make metals for ready use in odd places.

1. Based on this information, make assumptions about ‘A’ and ‘B’ and corresponding deductions about ‘C’ and ‘D’ and write a balanced chemical equation for the reaction.  Include in the chemical equation the physical states of the reactants and products, the need for heating to start the reaction, and the exothermic reaction.
2. Name two types of chemical reactions to which this reaction can belong.

Answer:

1. 

1. ‘A’ is aluminium, and ‘B’ is a ferric oxide (Iron (3) oxide).

2.

This reaction is a displacement reaction because ‘Al’ is displacing ‘Fe’. It is also a redox reaction because ‘Al’ is a reducing agent and Fe₂O₃ is an oxidising agent.

Question 10. Define activity series of metals. Arrange the metals gold, copper, iron and magnesium in order of their increase in reactivity.

1. What will you observe when:
2. Some zinc pieces are put in a copper sulphate solution.
3. Some silver pieces are put into a green-coloured ferrous sulphate solution.

Answer:

The series of metals in which metals are arranged in decreasing order of their reactivity.

Au < Cu < Fe < Mg is increasing order of reactivity.

The blue solution will become colourless and reddish-brown copper metal will be deposited.

⇒ \(\mathrm{Zn}(s)+\underset{\text { Blue }}{\mathrm{CuSO}_4(a q)} \longrightarrow \underset{\text { Colourless }}{\mathrm{ZnSO}_4(a q)}+\underset{\text { (reddish brown) }}{\mathrm{Cu}(s)}\)

Ag(s) + FeSO₄(aq) → No reaction

The reaction will not take place because ‘Ag’ is less reactive than iron.

Question 11. An ore on heating in the air, gives sulphur dioxide gas. Name the method in each metallurgical step, that will be required to extract this metal from its ore.

State which of the following reactions will take place or not, giving the suitable reason for each.

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

Fe(s) + ZnSO₄(aq) → FeSO₄(aq) + Zn(s)

Answer:

As the ore gives SO₂ on heating, it is sulphide ore.

Steps of metallurgy:

Concentration of ore by froth floatation process.

Conversion of sulphide ore into oxide by roasting.

Conversion of metal oxide to metal either by heating along or by reduction with carbon.

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

Yes, because Zn is more reactive than copper so will displace copper from the copper sulphate solution.

Fe(s) + ZnSO₄(aq) →FeSO₄(aq) + Zn(s)

No, because Fe is less reactive than Zn.

Question 12. How is the method of extraction of metals high up in the reactivity series different from that for metals in the middle? Why the same process cannot be applied to them? Explain giving equations, the extraction of sodium.
Answer:

Metals high up in the series are obtained by electrolytic reduction because these metals are strong reducing agents and therefore cannot be obtained by chemical reduction.

Metals in the middle of the series are less reactive and can be obtained by chemical reduction. The same process can’t be used for both of them as highly reactive metals can’t be obtained by chemical reduction.

Extraction of sodium is done by electrolysis of molten sodium chloride.

2 NaCl →(Electrolysis) → 2Na(s)+Cl₂(g)

Question 13.

1. Differentiate between roasting and calcination. Explain the two with the help of suitable chemical equations. How is zinc extracted from its ore?
2. Name two metals that can be used to reduce metal oxides to metals.

Answer:

1.

Roasting: It is a process in which sulphide ore is heated in the presence of oxygen to convert it into oxide.

2ZnS+ 3O₂→ 2ZnO + 2SO₂

Calcination: It is a process in which carbonate ore is heated in the absence of air to form oxide.

ZnCO₂(s) → (heat) → ZnO(s) + CO₂(g)

By reduction process, Zn can be extracted from its ore.

Reduction. ZnO+C → Zn + CO₂

2. Aluminium, Magnesium.

Metals and Non-Metals: NCERT Class 10 Science Key Concepts

Question 14.

1. State two methods to prevent the rusting of iron.
2.  Name the ores of the following metals
   1. Mercury, and
   2. Zinc
3. Explain with the help of a diagram, how copper metal can be refined. Label the important arrangements in the experimental set-up.

Answer:

1.

1. Painting
2. Galvanisation

2.

1. Cinnabar
2. Zinc Blende

3. Impure copper is taken as an anode whereas pure copper is taken as a cathode. Copper sulphate solution (CuSO₄) is taken as an electrolyte. When an electric current is passed, impure copper changes to ions which gain electrons at the cathode and change into pure copper. Impurities are left behind as anode mud.

At anode: Cu(s) → Cu²⁺ (aq) + 2e^–  Impure →

At cathode: Cu²⁺ (aq) + 2e^– → Cu(s)(Pure)

Question 15.

1. What are amphoteric oxides? Give two examples.

2. State reasons for the following:

1. Silver and copper lose their shine when they are exposed to air. Name the substance formed on their surface in each case.
2. Tarnished copper vessels are cleaned with tamarind juice.
3. Aluminium is more reactive than iron yet there is less corrosion of aluminium as compared to iron when both are exposed to air.

Answer:

Those oxides react with both acid as well as base to produce salt and water

Example: Al₂O₃, and ZnO.

1. These metals get corroded. Silver forms black Ag₂S (silver sulphide) and copper forms a greenish layer of basic copper carbonate CuCO₃.Cu(OH)₂.
2. Tamarind contains acid which reacts with basic copper carbonate and the product gets dissolved and removed from the copper vessel.
3. Aluminium forms an oxide layer on its surface which does not further react with air.

Question 16. Samples of four metals A, B, C, and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.

NCERT Solutions for Chapter 3: Metals and Non-Metals Detailed Explanation

Use the Table above to answer the following questions about metals A, B, C, and D.

1. Which is the most reactive metal?
2. What would you observe if B is added to a solution of Copper (II) sulphate?
3. Arrange the metals A, B, C, and D in the order of decreasing reactivity.

Answer:

1. B is the most reactive metal. From the table, B can displace iron from its solution, but others cannot.

2. B is more reactive than iron which is more reactive than copper. Hence B is more reactive than copper and displaces copper from its solution.

3. Thus, one will observe that the blue colour of copper sulphate fades away and red-brown particles of copper settle at the bottom of the container.

B > A > C > D.

Question 17.

1. Write the electron-dot structures for sodium, oxygen and magnesium.
2. Show the formation of Na₂O and MgO by the transfer of electrons.
3. What are the ions present in these compounds?

Answer:

1. Electron-dot structures of sodium, oxygen and magnesium:

2.

Formation Of Na₂O by The Transfer of electron:

Formation Of MgO by The Transfer of electron:

3.

1. Sodium (Na) and Oxide ion (O^2-) are present in Na, O.
2. Magnesium ion (Mg²⁺) and Oxide ion (O^2-)) are present in MgO.

Question 18. Define the terms:

1. Mineral
2. Ore
3. Gangue

Answer:

1. Mineral:

The naturally occurring compounds of metals which are generally mixed with other matter such as soil, rocks and limestone are called minerals.

2. Ore:

The minerals which contain a high percentage of the metal and the metal can be extracted profitably, i.e., with low cost and minimum effort, are called ores.

3. Gangue:

The impurity of sand, rocking materials and other contaminations present in the ore is called gangue.

Question 19. What chemical process is used to obtain a metal from its oxide?
Answer:

A chemical process called reduction is used to obtain a metal from its oxide. Zinc oxide is reduced to metallic zinc by heating with carbon.

⇒ \(\mathrm{ZnO}(\mathrm{s})+\mathrm{C}(\mathrm{s}) \longrightarrow \mathrm{Zn}(\mathrm{s})+\mathrm{CO}(\mathrm{g})\)

Sometimes displacement processes can also be used. Highly reactive metals like sodium, calcium, aluminium, etc., are used as reducing agents because these displace metals of low reactivity from their compounds,

Example:

2Al(s) + Fe₂O₃(s) → (Heat)→ Fe(s) + Al₂O₃(S).

Question 20. Metallic oxides of zinc, magnesium and copper were heated with the following metals:

Answer:

Class 10 Science Chapter 3: Metals and Non-Metals Practice Questions

Question 21. Give reasons

1. Platinum, gold and silver are used to make jewellery.
2. Sodium, potassium and lithium are stored under oil.
3. Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
4. Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Answer:

1. Because Pt, Au and Ag do not react with SO₂, CO₂ and H₂S gas present in the air and hence their glow is retained.
2. Sodium, potassium and lithium are stored under oil because they vigorously react with oxygen in the air and even catch fire.
3. Yes, aluminium is a reactive metal, still, it is being used to make utensils for cooking. This is because aluminium forms a non-reactive layer of aluminium oxide which resists spoiling any food material.
4. Carbonate and sulphide ores are usually converted into oxides during the process of extraction because it is easier to obtain a metal from its oxide as compared to its carbonates and sulphides.

Question 22. Differentiate between metal and non-metal based on their chemical properties.
Answer:

Difference between metals and non-metals based on chemical properties.

Question 23.

1. Show the formation of MgO by the transfer of electrons.
2. Name the cation and the anion.
3. Write three properties of ionic compounds.

Answer:

1. 

2. 

1. Cation is positively charged [Mg²⁺]
2. Anion is negatively charged (O^2-).

3. A solution of ionic compounds contains ions since electricity conduction requires the movement of charged particles that conduct electricity.

1. Soluble in water.
2. Good conductor of electricity in a molten state and aqueous solution.
3. High melting and boiling points.

Question 24. Differentiate between roasting and calcination.
Answer:

Differentiate between roasting and calcination

Question 25. Name the ore of mercury. How is mercury extracted from its ore?
Answer:

HgS-Cinnabar.

First, HgS is converted into HgO.

Then, HgO is reduced to mercury on further heating.

Question 26. State reasons for the following

1. Metals conduct electricity.
2. Non-metals in general do not displace hydrogen from dilute acids.
3. Aluminium easily combines with oxygen but still it can be used for making kitchen utensils.

Answer:

1. Metals have electrons which are free to move.

2. A non-metal is an electron acceptor. It cannot supply electrons to H⁺ ions. Hydrogen can only be displaced from dilute acids if electrons are supplied to the H⁺ ions of the acid. The layer of aluminium oxide formed prevents the metal from further oxidation.

Question 27. A metal ‘X’ acquires a green colour coating on its surface on exposure to air.

1. Identify the metal ‘X’ and name the process responsible for this change.
2. Name and write the chemical formula of the green coating formed on the metal.
3. List two important methods to prevent the process.

Answer:

Metal is copper. The process is corrosion.

Basic copper carbonate [CuCO₃.Cu(OH)₂]

It should be coated with tin.

It should be mixed with other metals to form alloys.

Question 28. Differentiate between metals and non-metals based on their chemical properties.
Answer:

Differentiate between metals and non-metals based on their chemical properties

NCERT Class 10 Science Chapter 3: Metals and Non-Metals Review

Question 29. Write balanced chemical equations for the following reactions:

1. Dilute sulphuric acid reacts with aluminium powder.
2. Dilute hydrochloric acid reacts with sodium carbonate.
3. Carbon dioxide is passed through lime water.

Answer:

⇒ \(2 \mathrm{Al}(s)+3 \mathrm{H}_2 \mathrm{SO}_4(\text { dil. }) \longrightarrow \mathrm{Al}_2\left(\mathrm{SO}_4\right)_3(a q)+3 \mathrm{H}_2(\mathrm{~g})\)

⇒ \(\mathrm{Na}_2 \mathrm{CO}_3(\mathrm{~s})+2 \mathrm{HCl}(\text { dil. }) \longrightarrow 2 \mathrm{NaCl}(a q)+\mathrm{H}_2 \mathrm{O}(l)+\mathrm{CO}_2(g)\)

⇒  \(\underset{\text { Lime water }}{\mathrm{Ca}(\mathrm{OH})_2(a q)}+\mathrm{CO}_2(\mathrm{~g}) \longrightarrow \underset{\text { (White ppt.) }}{\mathrm{CaCO}_3(\mathrm{~s})}+\mathrm{H}_2 \mathrm{O}(l)\)

Question 30. Observe the two test tubes A and B in the diagram given below and answer the following questions

1. In which test tube will the reaction take place?
2. Write a balanced equation for the reaction.
3. Name the type of reaction.

Answer:

In the first test tube, the reaction will take place.

Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)

Displacement reaction

Question 31. What is meant by the reactivity series of metals? State which of the following chemical reactions will take place giving the suitable reason for each.

1. Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
2. Fe(s) + ZnSO₄(aq) → FeSO₄(aq) + Zn(s)
3. Zn(s) + FeSO₄(aq) → ZnSO₄(aq) + Fe(s)

Answer:

• A reactivity series is a series of metals arranged in the order of their decreasing reactivities (activities).
• The reaction will take place because Zn is above Cu in the activity series and is more reactive than Cu.
• The reaction will not take place as Fe is below Zn in the activity series and cannot displace Zn from its solution.
• The reaction will take place because Zn is more reactive than Fe.

Question 32. Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in the reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how can he identify the produced gas. Write chemical equations for both reactions.
Answer:

As the element is lustrous, it must be a metal. As it is divalent and reacts with NaOH with the formation of bubbles of a gas (H₂ gas), it must be zinc. Further, zinc also reacts with HCl acid with the evolution of the same gas H₂.

The gas can be identified by bringing a lighted candle near it when it burns with a popping sound. The reactions taking place are as follows:

⇒ \(\underset{\text { Zinc }}{\mathrm{Zn}}+\underset{\text { Sodium hydroxide }}{2 \mathrm{NaOH}} \longrightarrow \underset{\text { Sodium zincate }}{\mathrm{Na}_2 \mathrm{ZnO}_2}+\underset{\text { Hydrogen gas }}{\mathrm{H}_2}\)

⇒ \(\underset{\text { Zinc }}{\mathrm{Zn}}+\underset{\text { Hydrochloric acid }}{2 \mathrm{HCl}} \longrightarrow \underset{\text { Zinc chloride }}{\mathrm{ZnCl}_2}+\underset{\text { Hydrogen gas }}{\mathrm{H}_2}\)

Question 33. You are given a hammer, a battery, a bulb, wires and a switch.

1. How could you use them to distinguish between samples of metals and non-metals?
2. Assess the usefulness of these tests in distinguishing between metals and non-metals.

Answer:

1.

1. On hammering the metals and non-metals, metals would give thin sheets whereas non-metals would break down into pieces.
2. Using a bulb, a battery, wires a switch, etc., given, an arrangement of the type shown in the figure will be made.

When the sample of metals and non-metals is inserted one by one between the clips and switch is made on. The bulb will glow when the metal is inserted, whereas the bulb will not glow in the case of non-metal.

2. Method A seems to be quite authentic in making a difference between metals and non-metals.

Question 34. An alkali metal A gives a compound B (molecular mass = 40) on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B, and C and give the reaction involved.
Answer:

⇒ \(\underset{\begin{array}{c}
\text { Sodium } \\
\text { (Alkalimetal) }
\end{array}}{2 \mathrm{Na}}+\underset{\text { (B) }}{2 \mathrm{H}_2 \mathrm{O}} \longrightarrow \underset{\begin{array}{c}
\text { Sodium hydroxide } \\
\text { (Mol. mass }=40 \text { ) }
\end{array}}{2 \mathrm{NaOH}}+\mathrm{H}_2\)

⇒ \(\underset{(\mathrm{B})}{2 \mathrm{NaOH}}+\underset{\begin{array}{c}
\text { Aluminium } \\
\text { oxide }
\end{array}}{\mathrm{Al}_2 \mathrm{O}_3} \longrightarrow \underset{\begin{array}{c}
\text { Sodium aluminate } \\
\text { (Soluble in water) }
\end{array}}{2 \mathrm{NaAlO}_2(a q)}+\mathrm{H}_2 \mathrm{O}(l)\)

Question 35. Give the reaction involved during the extraction of zinc from its ore by

1. Roasting of zinc ore
2. Calcination of zinc ore

Answer:

1. \(\underset{\text { Zinc sulphide }}{2 \mathrm{ZnS}(\mathrm{s})}+\underset{\text { From air }}{3 \mathrm{O}_2(\mathrm{~g})} \frac{\text { Heat }}{\begin{array}{c}
\text { Presence of excess } \\
\text { of air }
\end{array}} \underset{\text { Zinc oxide }}{2 \mathrm{ZnO}(\mathrm{s})}+\underset{\text { Sulphur dioxide }}{2 \mathrm{SO}_2(\mathrm{~g})}\)

2. \(\underset{\text { Zinc carbonate }}{\mathrm{ZnCO}_3(s)} \frac{\text { Heat }}{\text { Absence of air }} \underset{\text { Zinc oxide }}{\mathrm{ZnO}(s)}+\underset{\text { Carbon dioxide }}{\mathrm{CO}_2(g) \uparrow}\)

NCERT Class 10 Science: Metals and Non-Metals – Important Notes

Question 36. A non-metal A which is the largest constituent of air, when heated with H₂ in a 1:3 ratio in the presence of catalyst (Fe) gives a gas B. On heating with O, it gives an oxide C. If this oxide is passed into water in the presence of air it gives an acid D which acts as a strong oxidising agent.

1. Identify A, B, C, and D
2. To which group of the periodic table does this non-metal belong?

Answer:

A = N₂ (Nitrogen)

B = NH₃ (ammonia)

C = NO (Nitrogen oxide)

D = HNO₃ (Nitric acid)

Element A belongs to group 15 of the periodic table.

Question 37. Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.
Answer:

Question 38. Explain the following

1. The reactivity of Al decreases if it is dipped in HNO₃
2. Carbon cannot reduce the oxides of Na or Mg
3. NaCl is not a conductor of electricity in a solid state whereas it does conduct electricity in an aqueous solution as well as in a molten state
4. Iron articles are galvanised
5. Metals like Na, K, Ca and Mg are never found in their free state in nature

Answer:

1. Due to the formation of a layer of oxide i.e., Al₂O₃.
2. Na or Mg are more reactive metals as compared to carbon.
3. In solid NaCl, the movement of ions is not possible due to its rigid structure but in aqueous solution or molten state, the ions can move freely.
4. To protect from corrosion
5. They are highly reactive

Question 39.

1. Given below are the steps for the extraction of copper from its ore. Write the reactions involved.

1. Roasting of copper sulphide(l)
2. Reduction of copper oxide with copper(1) sulphide(l)
3. Electrolytic refining

2. Draw a neat and well-labelled diagram for electrolytic refining of copper.

Answer:

1.

1. Roasting of sulphide ore

2. 2Cu₂S(s) + 3O₂(S) →  (Heat)→  2Cu₂O(S) + 2SO₂(g)

2Cu₂O+ CuS  →  (Heat)→  6Cu(s) + SO₂(g)

This reaction is known as auto-reduction.

3. Reaction for electrolytic refining

At cathode: \(\mathrm{Cu}^{2+}(a q)+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(s)\)

At anode: \(\mathrm{Cu}(s) \longrightarrow \mathrm{Cu}^{2+}(a q)+2 e^{-}:\)

2. Diagram for electrolytic refining of copper

Question 40. Two ores A and B were taken. On heating ore A gives CO₂, whereas, ore B gives SO What steps will you take to convert them into metals?
Answer:

Ore A is the carbonate of any metal (MCO). It can be converted into metal by calcination followed by smelting or electrolytic reduction depending upon the nature of a metal.

MCO(s) → (Heat)→ MO(s)+CO↑ (Calcination)

MO(s)+C → (Heat)→ M(s)+CO↑ (Reduction)

Ore of B is any metal sulphate. To obtain the metal from this ore, first roasting then reduction is done.

Reduction

Reaction → 2MS (s) + 3O₂(g) → 2MO (s) + 2SO₂ (g)

MO (s) + C (s) M (s) → CO (g)

Question 41. Explain the following

1. The reactivity of Al decreases if it is dipped in HNO₃.
2. Carbon cannot reduce the oxides of Na or Mg.
3. NaCl is not a conductor of electricity in a solid state whereas it does conduct electricity in an aqueous solution as well as in a molten state.
4. Iron articles are galvanized.

Answer:

When Al metal reacts with HNO₃, Al₂O₃ is formed which further gets deposited on aluminium metal. Hence, more Al metal is not available for the reaction because the Al₂O₃ layer is passive.

Na and Mg both metals are very reactive. These metals have more affinity towards oxygen than carbon. Hence, carbon cannot reduce the oxides of these metals.

In NaCl, ions are responsible for the conduction of electricity. In a solid state, ions are strongly held by the electrostatic force of attraction and are not free to move. In an aqueous state or molten state, ions are free to move so conduction of electricity takes place.

Galvanization is a process to protect the iron from rusting. Iron articles get rusted when come in contact with air and moisture.

Question 42. A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming.

1. Identify A, B, and C.
2. To which group of the periodic table does A belong?

Answer:

As per the given information, non-metal A is carbon. It is an important constituent of our food (like carbohydrates, fat, protein). It forms two oxides-carbon monoxide which is toxic and carbon dioxide which in excess causes global warming.

A = Carbon (C)

B = Carbon monoxide (CO)

C = Carbon dioxide (CO₂)

A belongs to 14 groups of the periodic table

6C = 2.4

Group Number = Valence e+ 10 (for non-metals) = 4 + 10 = 14

Question 43. Nidhi and Nishi were visiting Qutub Minar along with their classmates. After seeing Qutub Minar, they went to see an iron pillar nearby. Nidhi said to Nishi, “Look this pillar was made around 400 BC as history says. But this has not rusted. What could be the technology behind this?” Nishi replied, “Yes this is amazing. Let us ask madam, how could the technicians of that era make such a wonder.”

1. What possibly was stated by Madam to the queries of Nidhi and Nishi?
2. How do the electrical conductivity and melting point of metals change when they are mixed to form an alloy?

Answer:

A thin layer of magnetic oxide was formed on the surface as a result of the finishing treatment given to the pillar. The pillar was painted with a mixture of different salts and then heated and quenched.

The electrical conductivity and melting point decrease on alloying the metals.

Question 44. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in the figure.

1. What will be the action of gas on

1. Dry litmus paper?
2. Moist litmus paper?

2. Write a balanced chemical equation for the reaction taking place.
Answer:

1.

1. No action on dry litmus paper.
2. Moist litmus paper becomes red as the gas is acidic.

2. The balanced equation for the reaction taking place:

⇒ \(\underset{\text { Sulphur }}{\mathrm{S}}+\underset{\text { Oxygen }}{\mathrm{O}_2(g)} \longrightarrow \underset{\begin{array}{c}
\text { Sulphur } \\
\text { dioxide }
\end{array}}{\mathrm{SO}_2}\)

Question 45. A jeweller made jewellery of 22-carat gold and also charged his customers the rate of

1. Why can’t we make jewellery out of 24-carat gold?
2. Name two metals that can be added to make gold jewellery.
3. What value of the jeweller is seen in the above act?

Answer:

1. Pure 24-carat gold is very soft and cannot retain the shape and design given to it while making the jewellery. Hence it is not advised to make use of 24-carat gold jewellery.
2. Copper and silver can be added to gold to make it strong and use it for making jewellery designs.
3. Jeweller is showing the value of honesty and faithfulness.

NCERT Solutions for Metals and Non-Metals: Chemical Properties and Applications

Question 46. A group of students presented a speech in the school assembly on “How to minimize the use of heavy metals?” They told how mercury thermometers when broken and thrown away in the garbage lead to soil and underground water pollution. They also showed how cadmium and lead also cause dangerous health problems.

1. Name two heavy metals that are present in the mobile batteries.
2. Name the disease caused due to mercury entering into our food chain.
3. What value of the group of students is reflected above?

Answer: 

1. Lead and cadmium are used in the mobile batteries.
2. Mercury causes Minamata disease.
3. The students showed the value of group work, cooperative learning, concern for nature and responsible behaviour.

Question 47. The use of aluminium foil occurs during lunch breaks. Eco-club suggests minimising the use of foils and rests all ensured to put it into dustbin for recycling.

1. Why is aluminium metal used for making foils?
2. Give one more use of aluminium metal with its quality being utilised in that use.
3. What values did eco-club members show?

Answer:

1. Aluminium metal is a very malleable metal and can be drawn into thin sheets. It also forms a protective layer of aluminium oxide which does not allow the foil to react with food.
2. Aluminium is a good conductor of electricity and is very ductile metal, it can be drawn into thin wires.
3. Eco-club members showed the value of group work, collaborative approach and aware and responsible citizens.

NCERT Solutions For Class 10 Science Chapter 1 Chemical Reactions And Equations Long Question And Answers

Question 1.

1. What is rancidity? Mention any two ways by which rancidity can be prevented.

2.

1. Why is respiration considered an exothermic reaction?
2. Define the terms—oxidation and reduction.
3. Identify the substance that is oxidised and reduced in the reaction:

CuO(s) + Zn(s) → Cu(s) + ZnO(s)

Answer:

1. The process in which the taste and smell of food get spoiled is called rancidity. It happens due to oxidation.

Prevention from rancidity:

• Antioxidants are added to fatty acids to prevent oxidation, e.g., chips are packed in the presence of nitrogen gas which prevents spoilage by oxidation.
• Food should be kept in an airtight container in the refrigerator.

2.

1. This is because heat is evolved during respiration.
2. Oxidation is a process in which O₂ is added or H₂ is removed or loss of electrons takes place.  Reduction is a process in which H₂ is added or O₂ is removed or a gain of electrons takes place.
3. Zn is getting oxidised, and CuO is getting reduced.

Chemical Reactions and Equations NCERT Class 10 Science Solutions

Read and Learn More Class 10 Science Solutions

Question 2.

1. 2 g of ferrous sulphate crystals are heated in a boiling tube.

1. State the colour of ferrous sulphate crystals both before heating and after heating.
2. Name the gases produced during heating.

2.  Give reasons for the following:

1. All decomposition reactions are endothermic reactions.
2. The colour of copper sulphate solution changes when an iron nail is dipped in it.
3. Respiration is an exothermic reaction.

Answer:

1.

1. Before heating- Pale green. After heating- Brown or reddish brown.
2. SO₂ and SO₃

2.

1. Decomposition reactions require energy either in the form of heat, light or
   electricity for breaking down the reactants or energy is absorbed.
2. Iron has displaced copper from the copper sulphate solution to form iron sulphate
   which is light green. Fe is more reactive than copper.
3. During digestion, food (rice, potatoes etc.) containing carbohydrates are broken down to form glucose. This glucose combines with oxygen in the cells of our body and provides energy. Since energy is given so it is an exothermic.

Question 3.

1. Write one example for each decomposition reaction

1. Electricity
2. Heat
3. Light

2. Which of the following statements is correct and why copper can displace silver from silver nitrate and silver can displace copper from copper sulphate solution

Answer:

1.

1. 2H₂O  → (Electricities)→ 2H₂(g) +O₂
2. CaCO₃ → (Heat) → CaO+CO₂
3. 2AgBr → (Sunlight) → 2Ag +Br₂

2. Copper can displace silver from AgNO₃ because copper is more reactive than Ag,

Example: Cu + 2AgNO₃(aq)→ Cu(NO₃)₂ (aq) + 2Ag (s)

NCERT Class 10 Science Chapter 1: Chemical Reactions and Equations Summary

Question 4.

1. Define corrosion.
2. What is corrosion of iron called?
3. How will you recognise the corrosion of silver?
4. Why corrosion of iron is a serious problem?
5. How can we prevent corrosion?

Answer:

1. Define Corrosion:  The process in which metals break down gradually by the action of air, moisture or a chemical on their surface.
2. Rusting of iron.
3. By the development of a black coating on silver.
4. Even- year enormous amount of money is spent to replace damaged iron.
5. Paint, or galvanisation, or electroplating.

Question 5. A metal nitrate ‘A’ on heating gives yellowish brown coloured metal oxide along with brown gas ‘B ‘and a colourless gas ‘C’ Aqueous solution of ‘A’ on reaction with potassium iodide forms a yellow precipitate of compound ‘D’. Identify ‘A, B, C, and D Also identify the types of h reactions. The metal present in ‘A’ is used in the alloy which is used for soldering purposes.
Answer:

Metal nitrate A is Pb(NO₃)₂.

A’ is lead nitrate, ‘B’ is nitrogen dioxide, ‘C’ is oxygen and ‘D’ is lead.

• Is decomposition reaction and
• Is a double displacement reaction (Precipitation reaction

NCERT Solutions Chapter 1: Chemical Reactions and Equations Questions and Answers

Question 6. Translate the following statement into chemical equations and then balance them.

1. Hydrogen gas combines with nitrogen to form ammonia.
2. Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.
3. Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
4. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
5. Aluminium chloride reacts with ammonium hydroxide to form a gelatinous white precipitate of aluminium hydroxide and a salt of ammonium chloride.

Answer:

1. \(3 \mathrm{H}_2(g)+\mathrm{N}_2(g) \Longrightarrow 2 \mathrm{NH}_3(g)\)

2. \(2 \mathrm{H}_2 \mathrm{~S}(g)+3 \mathrm{O}_2(g) \longrightarrow 2 \mathrm{SO}_2(g)+2 \mathrm{H}_2 \mathrm{O}(g)\)

3. \(3 \mathrm{BaCl}_2(a q)+\mathrm{Al}_2\left(\mathrm{SO}_4\right)_3(a q) \longrightarrow 2 \mathrm{AlCl}_3(a q)+3 \mathrm{BaSO}_4(s) \)

4. \(2 \mathrm{~K}(s)+2 \mathrm{H}_2 \mathrm{O}(l) \longrightarrow 2 \mathrm{KOH}(a q)+\mathrm{H}_2(g) \)

5. \( \mathrm{AlCl}_3(a q)+3 \mathrm{NH}_4 \mathrm{OH}(a q) \longrightarrow \mathrm{Al}(\mathrm{OH})_3(s) \downarrow+2 \mathrm{NH}_4 \mathrm{Cl}(a q)\)

Question 7. Give reasons why:

1. Sodium acts as a reducing agent while chlorine acts as an oxidising agent in the following reactions: 2Na(s)+Cl₂ (g)→ 2 NaCl(s)
2. White-coloured silver chloride turns grey when kept in sunlight.
3.  Why is the decomposition reaction called the opposite combination reaction?

Answer:

1. Sodium reduces chlorine atoms to chloride ions, therefore it acts as a reducing agent while chlorine oxidises sodium atoms to sodium ions, therefore, it acts as an oxidising agent

2. This is due to the decomposition of silver chloride into silver and chlorine by light.

3. In a decomposition reaction, one substance [compound] splits to give two or more simpler substances [elements or compounds] whereas in a combination reaction, two or more substances [elements or compounds] combine to form a single substance. Due to this reason, a decomposition reaction is called the opposite of a combination reaction.

Question 8. Observe the given figure and answer the following questions:

1. Write the complete balanced reaction for the above.
2. Write the type of reaction involved.
3. Is there any precipitate formed?
4. If any precipitate formed, write the colour of the precipitate.

Answer:

1. Na₂SO₄(ag) + BaCl₂(aq) →2NaCl(aq) + BaSO₄(s)↓ (White precipitate)

2. Double displacement reaction

3. Yes.

4. White precipitates of barium sulphate is formed.

NCERT Solutions Chapter 1: Chemical Reactions and Equations Questions and Answers

Question 9. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

1. Nitrogen gas is treated with hydrogen gas in the presence ofa catalyst at 773K to form ammonia gas.
2. Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.
3. Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of
   concentrated H₂SO₄
4. Ethene is burnt in the presence ofoxygen to form carbon dioxide, and water and releases heat and light.

Answer:

Example of a combination reaction.

2. NaOH(aq) + CH₃COOH(aq) → CH₃COOH(aq) + H₂O(l)

Example of neutralisation reaction as well as double displacement reaction.

3. C₂H₅OH(l) + CH₃COOH(Z) → H⁺  → CH₃COOC₂H₅ (l) + H₂O(Z)

Example of displacement reaction/Esterification

4. 2CH₃– CH₃(g) + 7O₂→ 4CO₂ + 6H₂O + Heat

Example of combustion reaction.

Question 10. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

1. In thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.
2. Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
3. Chlorine gas is passed in an aqueous potassium iodide solution to form a potassium chloride solution and solid iodine.
4. Ethanol is burnt in the air to form carbon dioxide, water and releases heat.

Answer:

1. Fe₂O₃(s) + 2Al(s)- Al₂O₃(S) + 2Fe(Z) + Heat

Displacement reaction/Redox reaction

2. 3Mg(s) + N₂(g) – Mg₃N₂(s)

Combination reaction

3. 2KI(aq) + Cl₂(g) – 2KCl(aq) + I₂(s)

Displacement reaction

4. C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l) + Heat

Redox reaction/Combustion reaction

NCERT Class 10 Science Chapter 1: Chemical Reactions and Equations Key Concepts

Question 11. During the reaction of some metals with dilute, hydrochloric acid following changes were made:

1. Silver metal does not show any change.
2. The temperature of the reaction mixture rises when aluminium (Al) is added.
3. The reaction of sodium metal is found to be highly explosive.
4. Some bubbles ofa gas are seen when lead (Pb) is reacted with the acid.
5. Explain these observations giving suitable reasons.

Answer:

1. Silver is below hydrogen in the reactivity series so it cannot displace hydrogen when reacted with acid.

2. The reaction of Al with dilute HC1 is exothermic

2Al + 6 HCl→ 2AlCl₃ + 3H₂ + Heat

3. Sodium is a very reactive metal. It reacts with hydrochloric acid to form NaCl and H₂ with the evolution of heat too. H₂ gas produced catches fire immediately.

4. Lead is slightly more reactive and displaces hydrogen from acid very slowly and to a small extent. Hence, only bubbles of H₂ can be seen

PbCl₂ + 2HCl → PbCl₂ + H₂ (g)

Question 12. Write a balanced chemical equation for each ofthe following reactions and also classify them.

1. Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.
2. Ca(OH)₂(aq)
3. A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.
4. Iron (3) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.
5. Hydrogen sulphidegas reacts with oxygen gas to form solid sulphur and liquid water.

Answer:

Pb (CH₃COO)₂ + 2HCl→PbCl₂ + CH₃ COOH; Double displacement reaction

2Na + 2C₂H₅OH→ 2C₂H₅ONa + H₂; Displacement reaction

Fe₂O₃ + 3CO → 2Fe + 3CO₂ ; Redox reaction

2H₂ S + O₂ – 2S + 2H₂O; Redox reaction

Question 13. Balance the following chemical equations and identify the type of chemical reaction.

1. \(\mathrm{Mg}(s)+\mathrm{Cl}_2(g) \longrightarrow \mathrm{MgCl}_2(s) \)

2. HgO(s)→ (Heat)→  Hg(l)+O₂(g)

3. Na(s)+S(s)→ (Fuse)→ Na₂S(s)

4. \( \mathrm{TiCl}_4(l)+\mathrm{Mg}(s) \longrightarrow \mathrm{Ti}(s)+\mathrm{MgCl}_2(s)\)

5. \(\left(\text { e) } \mathrm{CaO}(s)+\mathrm{SiO}_2(s) \longrightarrow \mathrm{CaSiO}_3(s)\right. \)

6. H₂O₂(l)→(UV) → HO₂(l)+O₂(g)

Answer:

1. \(\mathrm{Mg}(s)+\mathrm{Cl}_2(g) \longrightarrow \mathrm{MgCl}_2(s)\)(Balanced) – Combination reaction

2. 2HgO(s)→ (Heat)→  2Hg(l)+O₂(g)- Decomposition reaction

3. 2Na(s)+S(s)→ (Fuse)→ Na₂S(s) – Combination reaction

4. \(\mathrm{TiCl}_4(l)+2 \mathrm{Mg}(s) \longrightarrow \mathrm{Ti}(s)+2 \mathrm{MgCl}_2\) – Displacement reaction

5.\(\mathrm{CaO}(\mathrm{s})+\mathrm{SiO}_2(\mathrm{~s}) \longrightarrow \mathrm{CaSiO}_3(\mathrm{~s})\) – Combination reaction

6. 2H₂O₂(l)→(UV) → 2HO₂(l)+O₂(g) – Decomposition reaction

Chemical Reactions and Equations NCERT Class 10 Science Explanation and Notes

Question 14. On heating a blue-coloured powder of copper (II) nitrate in a boiling tube, copper oxide(black), oxygen gas and a brown gas X are formed.

1. Write a balanced chemical equation ofthe reaction.
2. Identify the brown gas X evolved.
3. Identify the type ofreaction.
4. What could be the pH range of the aqueous solution ofthe gas X?

Answer:

1. Balanced chemical equation

2Cu(NO₃)₂(s) →(Heat) → 2CuO (s) + O₂(g) + 4NO₂(g)

2. The brown pas X evolved is nitrogen dioxide (NO₂).

3. This is a decomposition reaction.

4. Nitrogen dioxide dissolves in water to form an acidic solution because it is an oxide of non-metal. Therefore, pH of this solution is less than 7.

Question 15. Give the characteristic tests for the following gases

1. CO₂
2. SO₂
3. O₂
4. H₂

Answer:

1. CO₂ gas turns lime water milky when passed through.
2. SO₂ gas when passed through an acidic KMnO₄ solution (purple) turns
   colourless.
3. The evolution of oxygen (O₂) gas during a reaction can be confirmed by bringing a burning candle near the mouth ofthe test tube containing the reaction mixture.The intensity of the flame increases because oxygen supports burning.
4. H₂ gas burns with a pop sound when a burning candle is brought near it.

Chemical Reactions and Equations NCERT Class 10 Science Explanation and Notes

Question 16. What happens when a piece of

1. Zinc metal is added to copper sulphate solution1?
2. Aluminium metal is added to dilute hydrochloric acid.
3. Silver metal is added to copper sulphate solution?

Also, write the balanced chemical equation if the reaction occurs.

Answer:

1. Zinc being more reactive than copper displaces copper from its solution and a solution of zinc sulphate is obtained

⇒ \(\underset{\text { Zinc }}{\mathrm{Zn}(s)}+\underset{\text { Copper sulphate(Blue) }}{\mathrm{CuSO}_4(a q)} \longrightarrow \underset{\text { Zinc sulphate(Colourless) }}{\mathrm{ZnSO}_4(a q)}+\underset{\text { Copper }}{\mathrm{Cu}(s)}\)

2. Aluminium being more reactive displaces hydrogen from dilute hydrochloric acid solution and hydrogen gas is evolved.

⇒ \(\underset{\text { Aluminium }}{2 \mathrm{Al}(s)}+\underset{\text { Hydrochloric acid}}{6 \mathrm{HCl}(a q)} \longrightarrow \underset{\text { Aluminium chloride}}{2 \mathrm{AlCl}_3(a q)}+\underset{\text { Hydrogen }}{3 \mathrm{H}_2(g)}\)

3. Silver metal being less reactive than copper cannot displace copper from its salt solution. Therefore, no reaction occurs

⇒ \(\underset{\text { Silver }}{\mathrm{Ag}(s)}+\underset{\text { Copper sulphate }}{\mathrm{CuSO}_4(a q)}\) → No reaction

Question 17. What happens when zinc granules are treated with a dilute solution of H₂SO₄, HCl, HNO₃, NaCl and NaOH? Also, write the chemical equations if a reaction occurs.
Answer:

The reaction of Zn granules with

1. Dilute H₂SO₄

Zn(s) + H₂SO₄(aq)→ ZnSO₄(aq) + H₂(g)

2. Dilute HCl

Zn(s) + 2HCl(aq)→ ZnCl₂(aq) + H₂(g)

3. Dilute HNO₃

4 Zn(s) + 10HNO₃ (aq) → 4Zn(NO₃)₂(aq) + 5 H₂O(l) + N₂O(g)

4. NaCl solution

Zn(s) + NaCl (aq ) → No reaction

5. NaOH solution

Zn(s) + 2NaOH(ag)→ Na₂ZnO₂(aq)( Sodium zincate) + H₂(g)

NCERT Solutions for Chemical Reactions and Equations Class 10 Science

Question 18. On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, a white precipitate is obtained

1. Write a balanced chemical equation of the reaction involved.
2. What other name can be given to this precipitation reaction?
3. On adding dilute HCl to the reaction mixture, the white precipitate disappears. Why?

Answer:

1. Balanced chemical equation

⇒ \(\underset{\text { Sodium sulphate }}{\mathrm{Na}_2 \mathrm{SO}_3(a q)}+\underset{\text { Barium chloride }}{\mathrm{BaCl}_2(a q)} \longrightarrow \underset{\text { Barium sulphite }}{\mathrm{BaSO}_3(s)}+\underset{\text { Sodium chloride }}{2 \mathrm{NaCl}(a q)}\)

2. This reaction is also known as a double displacement reaction.

3. BaSO₃ is a salt ofa weak acid (H₂SO₃), therefore dilute acids such as HCl decompose barium sulphite to produce sulphur dioxide gas which has the smell of burning sulphur

⇒ \(\underset{\text { Barium sulphite }}{\mathrm{BaSO}_3(s)}+\underset{\begin{array}{c}
\text { Hydrochloric } \\
\text { acid }
\end{array}}{2 \mathrm{HCl}(a q)} \longrightarrow \underset{\begin{array}{c}
\text { Barium } \\
\text { chloride }
\end{array}}{\mathrm{BaCl}_2}+\underset{\text { Water }}{\mathrm{H}_2 \mathrm{O}}+\underset{\begin{array}{c}
\text { Sulphur } \\
\text { dioxide }
\end{array}}{\mathrm{SO}_2(g)}\)

BaCl₂ is soluble in water, hence white precipitate disappears.

Question 19. You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO₃, ZnCl₂, and H₂O. In which of the above containers these solutions can be kept?

Answer:

1. When solutions are kept in a copper container

⇒ Dilute HCl

Copper does not react with dilute HCl. Therefore, it can be kept.

⇒  Dilute HNO₃

Nitric acid acts as a strong oxidising agent and reacts with copper vessels, therefore cannot be kept.

⇒  ZnCl₂

Zinc is more reactive than copper (Cu) therefore, no displacement reaction occurs and hence can be kept.

⇒  H₂O

Copper does not react with water. Therefore, can be kept.

2. When solutions are kept in aluminium containers

⇒  Dilute HCl

Aluminium reacts with dilute HCl to form its salt and hydrogen is evolved.

Therefore, if cannot be kept.

2Al + 6HCl→ 2 AlCl₃ + 3H₂

⇒ Dilute HNO₃

Aluminium gets oxidised by dilute HN03 to form a layer of A1203 and can be kept

⇒ ZnCl₂

Aluminium being more reactive than zinc can displace zinc ions from tho solution.

Therefore, the solution cannot ho kept.

2Al + 3ZnCl₂→ 2AlCl₃ + 3Zn

⇒ H₂O

Aluminium does not react with cold or hot water. Therefore, water can be kept.

Aluminium is attacked by steam to form aluminium oxide and hydrogen

2Al(s) + 3H₂O →Al₂O₃(s) + 3H₂(g)

NCERT Solutions for Chemical Reactions and Equations Class 10 Science

Question 20. Translate the following statement into a chemical equation and then balance the equation: Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.
Answer:

By observing the products, water (H₂O) and sulphur dioxide (SO₂), we can conclude that only oxygen from the air reacts with hydrogen sulphide (H₂S).

Hydrogen sulphide + Oxygen

The skeletal equation for the reaction is:

⇒ \(\mathrm{H}_2 \mathrm{~S}+\mathrm{O}_2 \longrightarrow \mathrm{H}_2 \mathrm{O}+\mathrm{SO}_2\)

If we observe the equation we find that H and S atoms are equal on both sides of the equation. To balance O atoms multiply O₂ by \(\frac{3}{2}\) becomes 3 on each side of the equation.

⇒  \(\mathrm{H}_2 \mathrm{~S}+\frac{3}{2} \mathrm{O}_2 \longrightarrow \mathrm{H}_2 \mathrm{O}+\mathrm{SO}_2\)

To make the coefficients whole numbers, multiply the above equation by 2.

⇒ \(2 \times \mathrm{H}_2 \mathrm{~S}+\frac{3}{2} 3 \mathrm{O}_2 \longrightarrow \mathrm{H}_2 \mathrm{O}+\mathrm{SO}_2\)

⇒ \(2 \mathrm{H}_2 \mathrm{~S}+3 \mathrm{O}_2 \longrightarrow 2 \mathrm{H}_2 \mathrm{O}+2 \mathrm{SO}_2\)

In the above equation, there are 4 atoms of hydrogen, 2 atoms of sulphur and 6 atoms of oxygen on each side of the equation. Hence, the equation is balanced.

Question 21. The equation for the oxidation of ammonia is: NH₃ + O₂ →  N+ H₂O, Rewrite the equation in a balanced form.

Answer:

The skeletal equation is

NH₃ + O₂ → N₂ + H₂O

NH₃ contains a maximum number of atoms, so the atoms present in it are balanced first.

Multiply NH₃ by 2 to balance N atoms.

2NH₃ + O₂ →N₂ + H₂O

Multiply H₂O by 3 to balance H atoms.

2NH₃ + O₂ → N₂ + 3H₂O

Oxygen is balanced last of all. To balance oxygen atoms multiply O₂ by \(\frac{3}{2}\)

⇒ \(2 \mathrm{NH}_3+\frac{3}{2} \mathrm{O}_2 \longrightarrow \mathrm{N}_2+3 \mathrm{H}_2 \mathrm{O}\)

Since all the coefficients should be whole numbers, multiply the above equation by 2 in order to convert all the coefficients to whole numbers.

⇒ \(2 \times 2 \mathrm{NH}_3+\frac{3}{2} \mathrm{O}_2 \longrightarrow \mathrm{N}_2+3 \mathrm{H}_2 \mathrm{O}\)

4NH₃ + 3O₂ →  2N₂ + 6H₂O

This is a balanced equation. There are 4 nitrogen atoms, 12 hydrogen atoms and 6 oxygen atoms on each side of the equation.

Question 22. Translate the following statement into a chemical equation and then balance the equation: Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.
Answer:

Carbon disulphide + Oxygen (from air)-» Carbon dioxide + Sulphur dioxide

The skeletal equation for the reaction is

CS₂ +O₂→ CO₂+ SO₂

Multiply SO₂ by 2 to balance sulphur atoms.

CS₂ +O₂ →CO₂ + 2SO₂

Carbon atoms are already balanced.

To balance oxygen atoms multiply O₂ by 3 so that each side of the equation has 6 oxygen atoms.

CS₂ + 3O₂ → CO₂ + 2SO₂

This is a balanced equation. It has 2 sulphur atoms, 6 oxygen, atoms and 1 carbon atom on each side of the equation

Question 23. When copper (2) oxide is heated with hydrogen, copper metal and water are according to the equation: CuO + H₂ →Cu + H₂O

In this reaction, identify:

1. The substance which undergoes oxidation
2. The substance which undergoes reduction
3. The oxidising agent
4. The reducing agent

Answer:

1. Here, H₂ changes to H₂O This involves addition ofoxygen. Hence, H2 is oxidised to water.

2. In this reaction, CuO changes to Cu. This involves the removal of oxygen i.e., reduction.

Thus, Copper(2) oxide, CuO is reduced to Cu.

3. Here, CuO brings about the oxidation of H₂ by supplying oxygen. Hence, CuO is, an oxidising agent.

4. H₂ brings about a reduction of CuO. Hence, H₂ is, a reducing agent.

Class 10 Science Chapter 1: Chemical Reactions and Equations Practice Questions

Question 24. Give differences between displacement and double displacement reactions.
Answer:

Displacement reactions:

1. In these reactions, a more reactive element displaces a less reactive element from its salt solution.

In these reactions, a more reactive element displaces a less reactive element from its salt solution.

2. These reactions are usually slow and take longer time for their completion.

3. During these reactions usually change of colour takes place. e.g.,

⇒ \(\mathrm{Fe}(s)+\underset{\text { Blue }}{\mathrm{CuSO}_4(a q)} \longrightarrow \underset{\text { Light green }}{\mathrm{FeSO}_4(a q)}+\mathrm{Cu}(s)\)

Double displacement reactions:

In these reactions, there is an exchange of ions between two reactants.

These reactions are usually fast and take place instantaneously.

During these reactions usually, precipitates are formed, e.g.,

AgNO₃(aq) + NaCl(aq)→  AgCl(s)(White Precipitate)↓+ NaNO₃(aq)

Question 25. Translate the following statements into chemical equations and then balance them.

1. Hydrogen gas combines with nitrogen to form ammonia.
2. Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.
3. Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
4. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas

Answer:

1. H₂(g) + N₂(g) → NH₃(g)

Balanced equation: 3H₂ (g) + N₂(g)- 2NH₃(g)

2.  H₂S(g) + O₂(g) →  2H₂O(l) +2 SO₂(g)

Balanced equation: 2H₂S(g) + 3O₂(g) →  2H₂O(l) +2 SO₂(g)

3. BaCl₂(aq) + Al₂(SO₄)₃(aq)→AlCl₃ (aq) +  3 BaSO₄(s)

Balanced equation: 3BaCl₂(aq) + Al(SO₄)₃(aq)→  2AlCl₃(aq) + 3BaSO₄(s)

4. K(s) + H₂O(l) → KOH(aq) + H₂(g)

Balanced equation: 2K(s) + 2H₂O(l) — 2KOH(aq) + H₂(g)

Question 26. Balance the following chemical equations:

1. \(\mathrm{HNO}_3+\mathrm{Ca}(\mathrm{OH})_2 \longrightarrow \mathrm{Ca}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2 \mathrm{O}\)

2. \(\mathrm{NaOH}+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{Na}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O}\)

3. \(\mathrm{NaCl}+\mathrm{AgNO}_3 \longrightarrow \mathrm{AgCl}+\mathrm{NaNO}_3\)

4. \(\mathrm{BaCl}_2+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{BaSO}_4+\mathrm{HCl}\)

Answer:

Balanced equations are as follows:

1. \( 2 \mathrm{HNO}_3+\mathrm{Ca}(\mathrm{OH})_2 \longrightarrow \mathrm{Ca}\left(\mathrm{NO}_3\right)_2+2 \mathrm{H}_2 \mathrm{O} \)

2. \(2 \mathrm{NaOH}+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{Na}_2 \mathrm{SO}_4+2 \mathrm{H}_2 \mathrm{O}\)

3. \(\mathrm{NaCl}+\mathrm{AgNO}_3 \longrightarrow \mathrm{AgCl}^2+\mathrm{NaNO}_3 \text { (already balanced) } \)

4. \(\mathrm{BaCl}_2+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{BaSO}_4+2 \mathrm{HCl}\)

Question 27. Write the balanced chemical equation for the following and identify the type of reaction in each case.

1. Potassium bromide (aq) + Barium iodide (aq) → Potassium iodidei (aq) + Barium, bromides)

2. Zinc carbonate(s)→ Zinc oxide (s) + Carbon dioxide

3. Hydrogen (aq)+ Chlorine→ Hydrogen chloride(aq)

4. Magnesium(s) + Hydrochloric acid (aq)

Magnesium chloride(aq) + Hydrogen(aq)

Answer:

1. 2KBr(aq) + Bal₂(aq)→ 2KI(aq) + BaBr₂(s)

Type of Reaction: Double displacement reaction

2. ZnCOg(s)→ ZnO(s) + CO2(g)

Type of Reaction: Decomposition reaction

3. H₂(g) + Cl₂(g) — 2HCl(g)

Type of Reaction: Combination reaction

4. Mg(s) + 2HCl(aq)→ MgCl₂(aq) + H₂(g)

Type of Reaction: Displacement reaction

Chemical Reactions and Equations: NCERT Class 10 Science Solutions

Question 28.

1. Write the essential condition for the following reaction to take place:

2AgBr → 2Ag + Br₂ Write one application of this reaction.

2. Complete the following chemical equation of a chemical reaction:

2FeSO₄ →  (Heat)→  Fe₂O₃+……….+……….

3. What happens when water is added to quick lime? Write chemical equation

Answer:

1. 2 AgBr →  (Sunlight)→ 2Ag+Br

This reaction is used in photography

2. 2 FeSO₄ →(Heat) → FeO+SO₂+SO₃

Slaked lime is formed with a hissing sound and a lot of heat is evolved.

⇒ \(\mathrm{CaO}+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{Ca}(\mathrm{OH})_2+\text { Heat }\)

Question 29. A zinc plate was put into a solution of copper sulphate kept in a glass container. It was found that the blue colour of the solution gets fader and fader with time. After a few days when the zinc plate was taken out of the solution, several holes were observed in it

1. State the reason for changes observed on the zinc plate.
2. Write the chemical equation for the reaction involved.

Answer:

1. This is because zinc has displaced copper from CuSO₄. Zinc metal has been used to form zinc sulphate, therefore, a number of holes were observed.

2. \(\mathrm{Zn}(s)+\underset{\text { Blue }}{\mathrm{CuSO}_4(a q)} \longrightarrow \underset{\text { Colourless }}{\mathrm{ZnSO}_4(a q)}+\mathrm{Cu}(s)\)

Question 30. The following diagram displays a chemical reaction. Observe and answer the following questions:

1. Identify the type of chemical reaction that will take place and define it. How will the colour ofthe salt change?
2. Write the chemical equation ofthe reaction that takes place.
3. Mention one commercial use of this salt.

Answer:

1. Photochemical decomposition reaction. The reaction in which a compound breaks down into simple substances in the presence of light is called a photochemical decomposition reaction. The colour of salt will change from white to grey.

2. 2AgCl(s) → (Sunlight) → 2Ag(s)+Cl(g)

3. Silver chloride is used in photography

Question 31. A, B, and C are are three elements which undergo chemical reactions according to the following equation:

A₂O₃ + 2B→ B₂O₃ + 2A

3CSO₄ + 2B→ B₂(SO₄ )₃ + 3C

3CO + 2A → A₂O₃ + 3C

Answer the following questions with reasons:

1. Which element is the most reactive?
2. Which element is the least reactive1?
3. What are the types of reactions listed above?

Answer:

1. B as B displaces both A and C from their solution.
2. C as C, is displaced by both A and B.
3. Displacement reactions

Question 32. Observe the following diagram and answer the following questions that follow:

1. Identify the gases that evolved at the anode and cathode.
2. Why are the amounts ofgases collected in the two test tubes not the same volume?
3. What type ofreaction is this?

Answer:

1.

1. At the anode, oxygen gas is evolved.
2. At the cathode, hydrogen gas is evolved.

2. The amounts of gases collected in the two test tubes are of not the same volume because in water, hydrogen and oxygen are present in the ratio of 2: 1 by mass.

3. This reaction is a decomposition reaction.

Question 33. Write the chemical equation of the reaction in which the following changes have taken place with an example of each:

1. Change in colour
2. Change in temperature
3. Formation of precipitate

Answer:

1. Cu(s) + 2AgNO₃(aq)→ Cu(NO₃)₂(aq) + 2Ag

The solution will become blue in colour and shiny silver metal will be deposited.

2. NaOH + HCl → NaCl + H₂O + Heat

The temperature will increase because heat will evolve.

3. Pb(NO₃)₂ (aq) + 2KI (aq)→ Pbl₂(s) + 2KNO₃(aq)

A yellow precipitate of Pbl₂ will be formed.

NCERT Class 10 Science: Chemical Reactions and Equations Detailed Solutions

Question 34. Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Answer:

A decomposition reaction is considered as the opposite of a combination reaction because in a decomposition reaction, a single substance decomposes to produce two or more substances; whereas in a combination reaction, two or more substances combine to give a single substance.

Examples of decomposition reaction

1. \(\mathrm{NH}_4 \mathrm{Cl}(\mathrm{s}) \longrightarrow \mathrm{HCl}(\mathrm{g})+\mathrm{NH}_3(g)\)

2. \(\mathrm{CaCO}_3(\mathrm{~s}) \longrightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g})\)

Examples of combination reaction

1. \(\mathrm{NH}_3($ g $)+\mathrm{HCl}(\mathrm{g}) \longrightarrow \mathrm{NH}_4 \mathrm{Cl}(\mathrm{s})\)

2. \(\mathrm{CO}_2(\mathrm{~g})+\mathrm{CaO}(\mathrm{s}) \longrightarrow \mathrm{CaCO}_3(\mathrm{~s})\)

Question 35. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Answer:

Examples of decomposition reaction

1. Decomposition by the use of heat

⇒ \(\mathrm{CaCO}_3(a) → {\text { (Heat) }}→ \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g}) \text {, }\)

2. Decomposition by the use of electricity

⇒ \(2 \mathrm{H}_2 \mathrm{O}(\mathrm{l})→{\text { (Electricity) }} → 2 \mathrm{H}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g})\)

3. Decomposition by the use of light

⇒ \(2 \mathrm{AgCl}(\mathrm{s}) → {\text { (Sunlight) }} → 2 \mathrm{Ag}(\mathrm{s})+\mathrm{Cl}_2(g)\)

Question 36. What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Answer:

In displacement reactions, an element displaces or removes another element, whereas in double displacement reactions exchange of ions between the reactants takes place.

Example of displacement reaction:

1. \(\underset{\text { Iron }}{\mathrm{Fe}(s)}+\underset{\text { Copper sulphate }}{\mathrm{CuSO}_4(a q)} \longrightarrow \underset{\text { Iron sulphate }}{\mathrm{FeSO}_4(a q)}+\underset{\text { Copper }}{\mathrm{Cu}(s)}\)

In this, the element iron has displaced copper from its salt solution (copper sulphate).

Example of double displacement reaction:

2.  \(\underset{\text { Sodium sulphate }}{\mathrm{Na}_2 \mathrm{SO}_4(a q)}+\underset{\text { Barium chloride }}{\mathrm{BaCl}_2(a q)} \longrightarrow \underset{\text { Barium sulphate }}{\mathrm{BaSO}_4(s)}+\underset{\text { Sodium chloride }}{2 \mathrm{NaCl}(a q)}\)

In the above reaction, the exchange of ions has taken place, i.e., Na+ ion has replaced Ba²⁺ and vice versa.

Question 37. Explain the following in terms of gain or loss of oxygen with two examples each.

1. Oxidation
2. Reduction

Answer:

1. Oxidation: A chemical reaction in which a substance gains oxygen is called oxidation.

For example:

1. 2 Cu +O → (Heat)  → 2 CuO

Cu is oxidised to CuO

2.  2 Mg +O →  (Burn)→  2MgO

Mg is oxidised to MgO

2. Reduction: A chemical reaction in which a substance loses oxygen is called reduction.

For examples:

1.  ZnO+ C → Zn +CO

ZnO is reduced to Zn

2. CuO +H₂ → Cu +H₂O

CuO is reduced to MgO

NCERT Class 10 Science: Chemical Reactions and Equations Detailed Solutions

Question 38. Explain the following terms with one example each.

1. Corrosion
2. Rancidity

Or

What is rancidity? What is corrosion? Mention any two ways by which they can be prevented.
Answer:

1. Corrosion:

Due to the effect of moisture and acids, metals get corroded, i.e., metals particularly iron form a porous layer on the surface and thus get damaged. This effect is called corrosion. Corrosion causes damage to metal articles like car bodies, bridges, iron railings, ships and other substances of daily use. To prevent corrosion iron articles should be regularly painted, done oiling, etc.

2. Rancidity:

Fats and oils in food kept for a long time get oxidised and become rancid and the taste of food changes and causes infection upon eating. This is called rancidity.

To prevent rancidity, antioxidants (which prevent oxidation) are added to foods containing fats and oils. Rancidity can also be prevented by flushing out oxygen with an inert gas like nitrogen.

For example, Packets of food items like chips are flushed with nitrogen so that these can be used even after a long duration.

Question 39. What does one mean by exothermic and endothermic reactions? Give examples.

Or

Differentiate between exothermic and endothermic reactions? Write one example for each of these reactions in the form of a balanced chemical equation.
Answer:

Exothermic reactions: Chemical reactions in which energy is evolved (or given out) are known as exothermic reactions.

For example:

CO₂(s) + O(g) → CO₂(g) + 393.7 kJ (ΔH =- 393.7 kJ)

Endothermic reactions:

Reactions in which energy is absorbed are called endothermic reactions. For example.

C(s) + 2S(s) → + CS₂ – 92 kJ (ΔH = + 92 kJ)

Question 40. A shiny brown-coloured element ‘X’ on heating in air becomes black. Name the element ‘X and the black-coloured compound formed. (PBQ)

Or

A reddish-brown coloured metal, used in electrical wires, when powdered and heated strongly in an open china dish, its colour turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on the above information, answer the following questions:
Answer:

1. Name the metal and black-coloured substance formed.
2. Write balanced chemical equations for both reactions.

Answer:

Element ‘X’ = Copper (Cu)

Compound = Copper oxide (CuO)

⇒ \(\underset{\text { Brown }}{2 \mathrm{Cu}(s)}+\underset{\text { (from air) }}{\mathrm{O}_2} \longrightarrow \underset{\text { Black }}{2 \mathrm{CuO}}\)

Question 41. Complete the missing components/variables given as x and y in the following reactions.

1. Pb(NO₃)₂(aq) + 2KI(aq)→ Pbl₂(x) + 2KNO₃(y)

2. Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂ (aq)+ x(s)

3. Zn(s) + H₂SO₄(aq)→ ZnSO₄(x) + H₂(y)

4. CaCO₃(s)→  (x) →  CaO(s)+CO₂(g)

Answer: 

1. x → Solid(s), y → aqueous (aq)

2. x → 2Ag

3. x → Aqueous(aq) y gas (g)

4. x → heat

NCERT Solutions for Class 10 Science Chapter 1: Chemical Reactions and Equations

Question 42. Which among the following changes are exothermic or endothermic?

1. Decomposition of ferrous sulphate
2. Dilution of sulphuric acid
3. Dissolution of sodium hydroxide in water
4. Dissolution of ammonium chloride in water

Answer:

1. Endothermic reaction
2. Exothermic reaction
3. Exothermic reaction
4. Endothermic reaction

Question 43. Identify the reducing agent in the following reactions.

1. 4NH₃ + 5O₂ → 4NO + 6H₂O
2. H₂O + F₂→ HF +HOF
3. Fe₂O₃ + 3CO → 2Fe + 3CO₂
4. 2H₂+ O₂ → 2H₂O

Answer:

1. Ammonia (NH₃)
2. Water (H₂O) as F₂ is getting reduced to HF
3. Carbon monoxide (CO)
4. Hydrogen

Question 44. Identify the oxidising agent (oxidant) in the following reactions.

1. 2Mg +O₂→ 2MgO
2. CuSO₄ + Zn → Cu + ZnSO₄
3. V₂O₅ + 5Ca- →2V + 5CaO
4. 3Fe + 4H₂O
5. CuO + H₂→ Cu + H₂O
6. Pb₃O₄ + 8HCl 3PbCl₂ + Cl₂ + 4H₂O

Answer:

1. O₂
2. CuSO₄
3. V₂O₅
4. H₂O
5. CuO
6. Pb₃O₄

Question 45. A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by the emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.

1. Write the chemical formulae of X and Y.
2. Write a balanced chemical equation, whenX is dissolved in water.

Answer:

2Mg + O₂ →  2MgO

3Mg + N₂→ Mg₃N₂

X is MgO; Y is Mg₃N₂

MgO + H₂O → Mg(OH)₂

Question 46. Tarun visited a government hospital to meet his cousin. He saw the medicines in dark bottles were not stored properly. They were not kept away from light and heat. Tarun reported the issue to the medical doctor and was satisfied that all medicines are stored properly.

1. Why are some medicines stored in cool places in dark bottles?
2. Why do some medicines need cool place1?
3. What can we get from this act?

Answer:

1. Medicines when kept in sunlight or in high temperatures lose its chemical identity.
2. Some medicines if not stored at an appropriate temperature show chemical changes and become dangerous for health.
3. Tarun showed his responsibility of well-being.

Question 47. Hunny a student of class 10 visited the house of his uncle Mohit during the summer holidays. He found that all the water taps were rusted. Hunny suggested Uncle to use either chrome-plated or nickel plated taps in place of iron taps. Mohit accepted his suggestion for the future.

1. Why did iron taps get rusted?
2. Name an antirust solution.
3. Name the process involved in the chrome plating or nickel plating.
4. Mention the values associated with the above act.

Answer:

1. Articles made up of iron readily get rusted when kept in moisture or water.
2. Bisphenol
3. Electroplating
4. Use of scientific knowledge, and help of others.

NCERT Solutions for Class 10 Science Chapter 1: Chemical Reactions and Equations

Question  48.

1. Write one example for each ofthe decomposition reactions carried out with the help of:

1. Electricity
2. Heat 
3. Sunlight

Give balanced chemical equations in each case.

2. Which of the following statements is correct and why? Copper can displace silver from the solution of silver nitrate and silver can displace copper from the solution of copper sulphate.

Answer:

1.

1. Electricity: 2H₂O(g)→ (Electric/current )→ 2H₂(g) + O₂(g)
2. Heat: CaCO₃(s) → (Heat) → CaO(s) + CO₂
3.  Sunlight:  2AgCl(s) → (Sunlight)→ 2 Ag(s)+Cl₂(g)

2. Copper can displace silver from silver nitrate solution because it is more reactive than silver.

Cu(s) + 2AgNO₃(aq)→ Cu(NO₃)₂(aq) + 2Ag(s)

NCERT Solutions For Class 10 Science Chapter 2 Acids, Bases And Salts Long Question And Answers

Question 1.

1. Mention the pH range within which our body works. Explain how antacids give relief from acidity. Write the name of one such antacid.
2. Fresh milk has a pH of 6. How does the pH will change as it turns to curd? Explain your answer.
3. A milkman adds a very small amount of baking soda to fresh milk. Why does this milk take a longer time to set as curd?
4. Mention the nature of toothpaste. How do they prevent tooth decay? 

Answer:

1. Our stomach has a pH equal to 2. Antacids neutralise excess acid in our body and give relief from hyperacidity. Sodium hydrogen carbonate is one such antacid.
2. pH will decrease as it turns to curd because curd is acidic due to the presence of lactic acid.
3. It takes a longer time to set as curd as bacteria do not work well in the presence of sodium hydrogen carbonate, i.e., fermentation will take place slowly.
4. Toothpastes are basic. They neutralise the acid formed in the mouth which causes tooth decay.

Acids, Bases, and Salts NCERT Class 10 Science Solutions

Read and Learn More Class 10 Science Solutions

Question 2.

1. State the chemical properties on which the following uses of baking soda are based

1. As an antacid
2. As soda-acid fire extinguisher
3. To make bread and cake soft and spongy.

2. How is washing soda obtained from baking soda? Write a balanced chemical equation.

Answer:

1.

1. It is weakly basic and neutralises hyperacidity.
2. It liberates CO₂ with H₂SO₄, which extinguishes fire.
3. It liberates CO₂ on heating which makes bread and cake soft and spongy

2. 2NaHCO₃→ (Heat) → Na₂CO₃ + CO₂ + H₂O

Baking soda on heating gives sodium carbonate which on crystallisation from an aqueous solution gives washing soda,

Example:

Na₂CO₃ + 10H₂O → Na₂CO₃ .10H₂O

Question 3. State the reason for the following statements:

1. Tap water conducts electricity whereas distilled water does not.
2. Dry hydrogen chloride gas does not turn blue litmus red whereas dilute hydrochloric acid does.
3. During the summer season, a milkman usually adds a very small amount of baking soda to fresh milk.
4. For a dilution of acid, acid is added into water and not water into acid.
5. Ammonia is a base but does not contain a hydroxyl group.

Answer:

1. Tap water contains ions which conduct electricity, distilled water does not contain ions.
2. Dry HCl does not form ions but HCl gives H⁺ and Cl^–.
3. Baking soda does not allow milk to change to lactic acid which makes milk sour.
4. Adding water to acid is highly exothermic. Therefore, water is added to the acid very slowly with cooling.
5. Ammonia dissolves in water and forms OH^–. Therefore, it is basic.

NH₃ + H₂O→  NH⁺ + OH^–

NCERT Class 10 Science Chapter 2: Acids, Bases, and Salts Summary

Question 4. Equal lengths of magnesium ribbon are taken in two test tubes A and B. H₂SO₄ is added to test tube A and H₂CO₃ in test tube B in equal amounts.

1. Identify the test tube showing a vigorous reaction.
2. Give reasons to support your answer.
3. Name the gas liberated in both test tubes. How will you prove its liberation?
4. Write chemical equations for both reactions.
5. Out of the two acids taken above, which one will have a lower value and lower H⁺ concentration respectively?

Answer:

1. Vigorous reaction will be seen in test tube A.

2. It is because H₂SO₄ is a stronger acid than H₂CO₃

3.

1. Hydrogen gas is liberated in both the test tubes.
2. When we bring a burning candle near the evolving gas, it burns with a pop sound. This proves that the produced gas is hydrogen gas.

4.

Mg + H₂SO₄→ MgSO₄ + H₂

Mg + H₂CO₃→ MgCO₃ + H₂

5.

‘A’ (H₂SO₄) will have a lower pH.

‘B’ (H₂CO₃) will have a lower concentration of H⁺

Question 5. Write balanced chemical equations for the following:

1. Bleaching powder is kept open in the air.
2. Blue crystals of copper sulphate are heated.
3. Chlorine gas is passed through dry slaked lime.
4. Carbon dioxide gas is passed through lime water.
5. NaOH solution is heated with zinc granules

Answer:

1. \(\underset{\text { Bleaching powder }}{\mathrm{CaOCl}_2(s)}+\underset{\text { Carbon dioxide }}{\mathrm{CO}_2(g)} \longrightarrow \underset{\text { Calcium carbonate }}{\mathrm{CaCO}_3(s)}+\underset{\text { Chlorine }}{\mathrm{Cl}_2(s)}\)

2. (Blue) CuSO₄.5H₂O → (Heat) → CuSO₄ + 5H₂O

3.  \(\underset{\text { Dry slaked lime }}{\mathrm{Ca}(\mathrm{OH})_2}+\underset{\text { Chlorine }}{\mathrm{Cl}_2} \longrightarrow \underset{\text { Bleaching powder }}{\mathrm{CaOCl}_2}+\mathrm{H}_2 \mathrm{O}\)

4. \(\underset{\text { Lime water }}{\mathrm{Ca}(\mathrm{OH})_2}+\mathrm{CO}_2 \longrightarrow \underset{\text { Calcium carbonate(Milky ppts) }}{\mathrm{CaCO}_3}+\mathrm{H}_2 \mathrm{O}\)

5. 2NaOH + Zn→ (heat) →(Sodium zincate) Na₂ZnO₂ + (Hydrogen)H₂

Acids, Bases, and Salts NCERT Class 10 Chapter 2 Questions and Answers

Question 6.

1. Identify the acid and the base whose combination forms the common salt that you use in your food. Write the formula and chemical name of this salt. Name the source from where it is obtained.
2. What is rock salt? Mention its colour and the reason why it has this colour.
3. What happens when electricity passes through brine? Write the chemical equation for it.

Answer:

1. Hydrochloric acid and sodium hydroxide.

NaCl, sodium chloride, ocean water.

2. solid salt deposits are found in several parts of the world. These large crystals are called rock salt.

Brown, due to impurities

3. 2NaCl + 2H₂O →(Electricity) → 2NaOH +Cl₂ +H₂

Question 7.

1. Write the chemical name and chemical formula of washing soda.
2. How is it obtained from sodium chloride? Give equations ofthe reactions.
3. Why is it called a basic salt? Give it anyone use.

Answer:

1. Chemical name—Sodium carbonate

Formula- Na₂CO₃.10H₂O

2. NaCl + H₂O + CO₂ + NH₃→ NH₄Cl + NaHCO₃

Na₂CO₃+ 10H₂O→ Na₂CO₃.10H₂O

3. It is a basic salt because it gives a strong base of NaOH when it dissolves in water.

1. In glass and paper industry.
2. As cleaning agent.
3. To remove permanent hardness, (anyone)

NCERT Solutions for Chapter 2: Acids, Bases, and Salts Key Concepts

Question 8. A student dropped a few pieces of marble in dilute hydrochloric acid, contained in a test tube. The evolved gas was then passed through lime water. What change would be observed in lime water? What will happen if an excess of gas is passed through lime water? With the help of balanced chemical equations for all the changes explain the observations.

⇒ \(\underset{\text { Marble }}{\mathrm{CaCO}_3}+2 \mathrm{HCl}(\text { dil. }) \longrightarrow \underset{\text { Calcium chloride }}{\mathrm{CaCl}_2}+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2\)

Lime water will turn milky.

Ca(OH)₂(aq) + CO₂(g) CaCO₃(s) + H₂O(l)

If excess CO₂ gas passes through lime water, milkiness will disappear due to the formation of Ca(HCO₃)(aq) which is soluble in water.

CaCO₃(S) + H₂O(l) + CO₂(g) → Ca(HCO₃)₂(aq)

Question 9.

1. Explain why is hydrochloric acid a strong acid and acetic acid, a weak acid. How can it be verified?

2. Explain why an aqueous solution and an acid conduct electricity

3. You have four solutions A, B, C, and D. The solution A is 6, B is 9, C is 12 and D is 7.

1. Identify the most acidic and most basic solutions.
2. Arrange the above four solutions in the increasing order of H+ ion concentration.
3. State the change in colour of pH paper on dipping in solutions C and D.

Answer:

1. HCl is completely ionised in aqueous solution, whereas acetic acid is partially ionised in aqueous solution. HCl gives a dark red colour with pH paper, whereas CH₃COOH gives an orange colour.

2. It is because acid ionises in aqueous solution.

3.

1. ‘A’ is most acidic and ‘C’ is most basic.
2. C (10^-12) < B (10^-9) < D (10^-7) < A (10^-6)
3. pH of paper will become blue in ‘C’ and green in ‘D’.

NCERT Class 10 Science: Acids, Bases, and Salts Explanation and Notes

Question 10. Dry pellets ofa base ‘X’ when kept in open absorbs moisture and turns sticky. The compound is also formed by the chlor-alkali process. Write the chemical name and formula of X. Describe the chlor-alkali process with a balanced chemical equation. Name the type of reaction that occurs when X is treated with dilute hydrochloric acid. Write the chemical equation.

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Answer:

1. X is sodium hydroxide, NaOH.

When sodium chloride solution (brine solution) is electrolysed, sodium hydroxide solution is formed. H₂ and Cl₂ gases are liberated. This is a chlor-alkali process.

2NaCl + 2H₂O→ (Electrolysis) 2NaOH + H₂ + Cl₂

NaOH + HCl ↓  NaCl + H₂O

The above reaction is a neutralisation reaction.

2. It is because the process is highly exothermic. If water is added to acid, a bottle of acid will break.

Acids, Bases, and Salts: NCERT Class 10 Science Chapter 2 Review

Question 11. How do metal carbonates and metal hydrogen carbonates react with acids? Give their chemical equations. Name the gas that evolved during the reaction. What will happen when this gas is passed through lime water?
Answer:

1. Metal carbonate and hydrogen carbonate react with acids to give corresponding salt, carbon dioxide and water.

2.

Metal carbonate:

Na₂CO₃(s) + 2HCl(aq) →  2NaCl(aq) + H₂O(l) + CO₂(g)

Metal hydrogen carbonate:

NaHCO₃(s) + HCl(aq) – NaCl(aq) + H₂O(l) + CO₂(g)

3. The gas that evolved is carbon dioxide (CO₂).

4. When this gas is passed through lime water, it turns milky.

Question 12. Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?
Answer:

When an acid reacts with a metal, hydrogen gas is usually liberated.

For example:

⇒ \(\underset{\text { Zinc }}{\mathrm{Zn}(s)}+\underset{\begin{array}{c}
\text { Sulphuric } \\
\text { acid }
\end{array}}{\mathrm{H}_2 \mathrm{SO}_4(a q)} \longrightarrow \underset{\begin{array}{c}
\text { Zinc } \\
\text { sulphate }
\end{array}}{\mathrm{ZnSO}_4(a q)}+\underset{\text { Hydrogen }}{\mathrm{H}_2(g)}\)

⇒ \(\underset{\text { Magnesium }}{\mathrm{Mg}(s)}+\underset{\text { Hydrochloric acid }}{2 \mathrm{HCl}(a q)} \longrightarrow \underset{\text { Magnesium chloride }}{\mathrm{MgCl}_2(a q)}+\underset{\text { Hydrogen }}{\mathrm{H}_2(g)}\)

Question 13. Write word equations and then balanced equations for the reaction taking place when:

1. Dilute sulphuric acid reacts with zinc granules.
2. Dilute hydrochloric acid reacts with magnesium ribbon.
3. Dilute sulphuric acid reacts with aluminium powder.
4. Dilute hydrochloric acid reacts with iron filings.

Answer:

1.  Zinc + dil. sulphuric acid→ Zinc sulphate + Hydrogen

Zn + H₂SO₄→ ZnSO₄ + H₂

2. Magnesium ribbon + dil. hydrochloric acid→Magnesium chloride + Hydrogen

Mg + 2HCl→MgCl₂ + H₂

3. Aluminium powder + dil. sulphuric acid→Aluminium sulphate + Hydrogen

2Al + 3H₂SO₄→ Al₂(SO₄)₃ + 3H₂

4. Dilute hydrochloric acid + Iron filings→Iron chloride + Hydrogen

2Fe + 6HCl→ 2FeCl₃ + 3H₂

NCERT Solutions for Acids, Bases, and Salts Class 10 Science

Question 14. Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.
Answer:

Take solutions of alcohol, and glucose in a beaker.

Take a cork and fix two nails on the cork up to the end. Keep this cork in the beaker. Connect the nails to two terminals ofa the 6-volt battery through a bulb and a switch. Switch on the current. You will see that the bulb does not glow. This means no ions or H+ ions are present in the solution. This shows that alcohols and glucose are not acids.

Question 15. What is a neutralisation reaction? Give two examples.
Answer:

The reaction between an acid and a base to give salt and water is known neutralization reaction.

Base+Acid → Salt + Water

Examples:

⇒ \(\underset{\text { Hydrochloric acid (Acid) }}{\mathrm{HCl}}+\underset{\text { Sodium Hydroxide (base) }}{\mathrm{NaOH}} \longrightarrow \underset{\text { Sodium chloride (salt) }}{\mathrm{NaCl}}+\underset{\text { Water }}{\mathrm{H}_2 \mathrm{O}}\)

⇒  \(\underset{\text { Acetic acid (Acid) }}{\mathrm{CH}_3 \mathrm{COOH}}+\underset{\text { Sodium hydroxide (Base)}}{\mathrm{NaOH}} \longrightarrow \underset{\text { Sodium acetate(salt) }}{\mathrm{CH}_3 \mathrm{COONa}}+\underset{\text { Water }}{\mathrm{H}_2 \mathrm{O}}\)

Question 16.

1. What will you observe when dilute hydrochloric acid is added to a small amount of copper oxide in a beaker?
2. An aqueous solution of HCl shows an acidic character. However, the aqueous solution of glucose fails to do so. Why?
3. Why curd and sour substances not be kept in brass and copper vessels?

Answer:

1. The colour of the solution becomes blue and the copper oxide dissolves

CuO +2HCl → CuCl₂ + H₂O

2. Aqueous solution of HCl can produce H+ ions. Therefore, they show an acidic character.

However the aqueous solution of glucose does not produce H+ ions, i.e., they fail to evolve hydrogen gas and do not show any acidic character.

3. Curd and sour substances have acids which react with copper present in brass and form compounds which are poisonous.

Class 10 Science Chapter 2: Acids, Bases, and Salts Detailed Solutions

Question 17. Answer the following:

1. Why is Plaster of Paris written as CaSO₄.½H₂O? How is it possible to have half a water molecule attached to CaSO₄?
2. Why is sodium hydrogen carbonate an essential ingredient in antacids?
3. Three products are obtained when electricity is passed through an aqueous solution ofsodium chloride. Why is the process called chlor-alkali?

Answer:

1. It is written in this form because two formula units of CaS04 share one molecule of water.
2. Sodium hydrogen carbonate being alkaline, neutralises excess acid in the stomach and provides relief.
3. The process is called chlor-alkali because of the products formed—chlor for chlorine and alkali for sodium hydroxide.

Question 18. How would you distinguish between baking powder and washing soda by heating?
Answer:

The chemical formula of baking powder is sodium hydrogen carbonate (NaHCO₃). Whereas, that of washing soda is sodium carbonate (Na₂CO₃.10H₂O) Sodium hydrogen carbonate on heating gives CO₂ gas which will turn lime water milky whereas no such gas is obtained from sodium carbonate.

2NaHCO₃ → (Heat) →  Na₂CO₃ + H₃O + CO₂

Na₂CO₃.10H₂O →  (Heat) → Na₂CO₃+ 10H₂O

Question 19. Fill up the missing data in the following table

Answer: 

NCERT Class 10 Science Chapter 2: Acids, Bases, and Salts Practice Questions

Question 20. For making a cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake,

1. How will it affect the taste ofthe cake and. why?
2. How can baking soda be converted into baking powder?
3. What is the role of tartaric acid added to baking soda?

Answer:

1. Baking soda is sodium hydrogen carbonate. On heating, it is converted into sodium carbonate which is bitter to taste

2NaHCO₃→ (Heat) →Na₂CO₃+ H₂O + CO₂

2. Baking soda can be converted into baking powder by the addition of an appropriate amount of tartaric acid to it.

3. The role of tartaric acid is to neutralise sodium carbonate and cake will not taste bitter.

Question 21. A metal carbonate X reacting with acid gives a gas which when passed through a solution Ygives the carbonate back. On the other hand, a gas G that is obtained at the anode during electrolysis ofbrine ispassed on dry Y, which gives a compound Z, used for disinfecting drinking water. Identity X, Y, G, and Z.

And

Hence, X = CaCO₃, Y = Ca(OH₂, G = Cl₂, Z = CaOCl₂.

Question 22. A dry pellet ofa common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by-product of the chloralkali process. Identify B. What type ofreaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
Answer:

The common base B which absorbs moisture and becomes sticky and is also n by-product of the chloroalkali process is sodium hydroxide (NaOH). It reacts with acidic oxides like

⇒ \(2 \mathrm{NaOH}+\mathrm{CO}_2 \longrightarrow \underset{\text { Sodium carbonate }}{\mathrm{Na}_2 \mathrm{CO}_3}+\mathrm{H}_2 \mathrm{O}\).

⇒  \(2 \mathrm{NaOH}+\mathrm{SO}_2 \longrightarrow \underset{\text { Sodium sulphite }}{\mathrm{Na}_2 \mathrm{SO}_3}+\mathrm{H}_2 \mathrm{O}\).

NCERT Solutions for Class 10 Science Chapter 2: Acids, Bases, and Salts

Question 23. A sulphate salt of Group 2 element ofthe Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in the open for some time, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why it shows such a behaviour. Give the reaction involved.
Answer:

The substance which is used for making different shapes is Plaster of Paris. Its chemical name is calcium sulphate hemihydrate (CaSO₄. ½H₂O). The two formula units of CaSO₄ share one molecule of water.

As a result, it is soft. When it is left open for some time, it absorbs moisture from the atmosphere and forms gypsum, which is a hard solid mass.

⇒ \(\mathrm{CaSO}_4 \cdot \frac{1}{2} \mathrm{H}_2 \mathrm{O}+1 \frac{1}{2} \mathrm{H}_2 \mathrm{O}\)(Plaster of pairs )(Soft) (Sulphate salt) → \(\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}\) Gypsum(Hard mass)

Question 24. Identify the compound X based on the reactions given below. Also, write the name and chemical formulae ofA, B, and C.

Answer:

⇒ \(\underset{(\mathrm{X})}{2 \mathrm{NaOH}}+\mathrm{Zn} \longrightarrow \underset{(\mathrm{A})(Sodium zincate)}{\mathrm{Na}_2 \mathrm{ZnO}_2}+\mathrm{H}_2\)

⇒  \(\mathrm{NaOH}+\mathrm{HCl} \longrightarrow \underset{(\mathrm{B})(Sodium chloride)}{\mathrm{NaCl}} \quad+\mathrm{H}_2 \mathrm{O}\)

⇒  \(\mathrm{NaOH}+\mathrm{CH}_3 \mathrm{COOH} \longrightarrow \underset{\text { (C) Sodium acetate }}{\mathrm{CH}_3 \mathrm{COONa}}+\mathrm{H}_2 \mathrm{O}\)

Question 25. A metal carbonate (X) reacting with acid gives a gas which when passed through a solution (Y) gives the carbonate back. On the other hand, a gas (G) that is obtained at the anode during the electrolysis of brine is passed on dry substance (Y). It gives a compound (Z) used for disinfecting drinking water. Identify X, Y, G, and Z.
Answer:

Electrolysis of brine gives chlorine gas to the anode. It is gas G. This gas in reaction with slaked lime (Y) gives bleaching powder (Z) used in the disinfection of drinking water

Compound X is calcium carbonate which in reaction with acid gives calcium chloride and CO₂ gas. This CO₂ gas on reaction with Ca(OH)₂ gives compound (X) back

⇒ \(\underset{[\mathrm{X}]}{\mathrm{CaCO}_3}+\underset{\text { acid }}{2 \mathrm{HCl}} \longrightarrow \mathrm{CaCl}_2+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 \uparrow\)

⇒ \(\underset{[\text { Y] }}{\mathrm{Ca}(\mathrm{OH})_2}+\mathrm{CO}_2 \longrightarrow \underset{[\mathrm{X}]}{\mathrm{CaCO}_3}+\mathrm{H}_2 \mathrm{O}\)

⇒ \(\underset{[\mathrm{Y}]}{\mathrm{Ca}(\mathrm{OH})_2}+\underset{\text { obtained from brine solution }}{\mathrm{Cl}_2} \longrightarrow \mathrm{CaOCl}_2+\mathrm{H}_2 \mathrm{O}\)

NCERT Solutions for Class 10 Science Chapter 2: Acids, Bases, and Salts

Question 26. In the following schematic diagram for the preparation of hydrogen gas as shown in the figure, what would happen if the following changes are made?

1. In place of zinc granules, the same amount of zinc dust is taken in the test tube
2. Instead of dilute sulphuric acid, dilute hydrochloric acid is taken
3. In place of zinc, copper turnings are taken
4. Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.

Answer:

1. If zinc dust is taken, the reaction is faster because zinc dust has a larger surface area.
2. Both will react completely with the zinc to evolve the same amount of H₂ gas.
3. Copper does not react with dilute H₂SO₄ or dilute HCl. Hence, no reaction will occur.
4. Zinc also reacts with NaOH on heating to give out H₂ gas

Zn + 2NaOH → (Heat) →  Na₂ZnO₂ (Sodium zincate)+ H₂