NCERT Solutions For Class 11 Chemistry Chapter 14 Environmental Chemistry Short Answer Questions

NCERT Solutions For Class 11 Chemistry Chapter 14 Environmental Chemistry Short Question And Answers

Question 1. How are NO and NO₂ produced in the atmosphere?!
Answer:

Due to lightning discharge in the upper atmosphere, nitrogen and oxygen combine to produce nitric oxide. This nitric oxide (NO) reacts with aerial oxygen to give nitrogen dioxide.  (NO₂) Because of the bacterial decomposition of ammonium salts in the soil, NO is produced. Besides these, the combustion of fossil fuels also serves as a potential source of NO and NO_2.

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Question 2. In the presence of carbon monoxide, haemoglobin loses its oxygen-carrying capacity causing oxygen starvation of body cells—explain
Answer:

Carbon monoxide has a strong affinity for haemoglobin This gas combines with haemoglobin to form highly stable carboxy haemoglobin Consequently, the availability of oxygen in the body cells decreases, because haemoglobin fails to carry the oxygen necessary for the life process to continue. So carbon monoxide present in excess may sometimes cause death.

Question 3. Many spray bottles from which a perfume is sprayed contain a very harmful substance. By what name is it commonly known? Why is it harmful?
Answer:

The harmful constituent is chlorofluorocarbons (CFCs) or Freons. When they diffuse into the upper atmosphere, they absorb ultraviolet radiation which ruptures carbon-chlorine bonds to give chlorine atoms. The chlorine atoms thus produced cause destruction of the ozone layer which shields the earth from the harmful effects of ultraviolet radiation of the sun. This is the reason why CFCs are very harmful.

Question 4. What is hypothermia?
Answer:

Mineral oil and by-products of oil get dispersed in water for various reasons, thereby contaminating it. When a bird comes in contact with this polluted water, the oil floating on the surface of the water penetrates the feathers and wings of the bird. This in turn annihilates the possibility of the bird’s flight. In addition, the temperature of the bird’s body drops considerably, resulting in its death. This phenomenon is called hypothermia.

Question 5. What were the components of London Smog? What was its nature?
Answer:

Finely divided particles, water vapour, SOx and quantity of NO It was reducing in nature because the non-metallic oxide SO₂ was mainly present in it as a reducing agent

Question 6. It was reducing in nature because the non-metallic oxide, SO₂ was mainly present in it as a reducing agent
Answer:

O₃, NO₂ Peroxyacyl nitrate (PAN), aldehyde, ketone, hydrocarbons and CO. It was oxidising in character, because O₃, NO₂ peroxyacyl nitrate etc., were present in it as oxidising agents. Peroxyacetyl nitrate etc., were present in it as oxidising agents

Question 7. What is the temperature range of the atmosphere? What do you mean by inversion temperature in different regions of the atmosphere?
Answer:

-56°C to 1200°C . When we traverse from one region of the atmosphere to the next adjoining region, the trend of temperature changes successively from higher to lower or vice versa. This is called inversion temperature.

Question 8. What is marine pollution? What is siltation?
Answer:

The pollution of seawater due to the discharge of wastes from different sources into it thereby making it harmful to human health and aquatic life is called marine pollution. Mixing of soil and rock particles into water is called siltation. The soil particles produce turbidity in water thereby hindering the free movement of aquatic organisms.

Question 9. What is the Polar Vortex? What is its effect?
Answer:

A tight whirlpool of wind formed in the stratosphere surrounding Antarctica is called the Polar Vortex. It is so rigid that it cuts off Antarctica from the surrounding ozone-rich air of the non-polar regions. Thus, as long as the polar vortex surrounds Antarctica, the ozone hole remains unfilled.

Question 10. What is an ozone umbrella? Why is it called so?
Answer:

The ozone layer present in the stratosphere is called the ozone umbrella. Like an umbrella, the ozone layer prevents harmful. UV radiation from reaching the earth. Thus, the ozone layer is also called the ozone umbrella.

Question 11. In hospitals, patients with CO poisoning are kept in high-pressure chambers containing oxygen at 2 to 2.5 atm pressure—why?
Answer:

Under high pressure of oxygen, CO of carboxyhaemoglobin (HbCO) is replaced by O₂ and thus transport of O₂ to different parts of the body starts.

HbCO + O₂ ⇌  HbO₂+CO

Question 12. What is the role of CO₂ in creating the greenhouse effect?
Answer:

A part of the infrared rays of longer wavelength, emitted by the earth’s surface on being heated by the sun rays is absorbed by CO₂ gas molecules and the return to the earth’s surface along with the surrounding atmosphere gets heated.

Question 13. What are Polar Stratospheric Clouds (PSCs)?
Answer:

In Antarctica, the climatic conditions are quite different. In winter, there is no sunlight and the temperature is very low. The low temperature causes the formation of special types of clouds over Antarctica which are called Polar Stratospheric Clouds (PSCs).

Question 14. In which regions atmosphere, temperature increases with altitude and in which regions it decreases?
Answer:

• In the stratosphere and thermosphere temperature increases with altitude, while in the troposphere and mesosphere, temperature decreases with altitude.
• In which season the depletion of the ozone layer in Antarctica takes place and when is it replenished
• During spring (in September and October) ozone layer depletion occurs in Antarctica, while after spring.

The gaseous and particulate pollutants are:

1. Gaseous air pollutants: These are mainly oxides of sulphur (SO₂, SO₃), oxides of nitrogen (NO, NO₂) and oxides of carbon (CO, CO₂), H₂S, hydrocarbons, ozone and other oxidants.
2. Particulate pollutants: Particles in the form of smog, dust, mist, smoke etc., belong to this category

NCERT Solutions For Class 11 Chemistry Chapter 14 Environmental Chemistry Question And Answers

Question 1. What Is fly ash?
Answer:

Fly ash is emitted from thermal power plants due to the combustion of coal. It consists of fine particles of SiO_2.

Al₂O₃, CaO, Fe₂O₃, NO₂, SO₂, P₂O₃

Question 2. What are the sinks for CO₂ and CO gases?
Answer:

Sea water (CO₂ is soluble here) and some special bacteria (which absorb CO and convert it into CO₂

Question 3. Mention three hydrocarbons which function as air pollutants.
Answer:

1,3-butadiene, 1,2-benzopyrene, 1,2-benzanthracene

Question 4. Name three primary and three secondary air pollutants.
Answer:

1. Primary air pollutants: CO, SO₂, NO₂;
2. Secondary air pollutants: O₃, PAN, formaldehyde

Question 5. Name some hydrocarbons that are present in the atmosphere as organic particulates.
Answer:

Methane, benzene, benzopyrene

Question 6. Name the compounds responsible for ozone hole formation.
Answer:

Chlorofluorocarbons, halons etc

Question 7. Why does the temperature of the stratosphere increase with the increase in height?
Answer:

The ozone layer in the stratosphere absorbs the harmful ultraviolet radiation coming from the sun and converts it into heat. Thus the temperature of this layer increases.

Question 8. What are halons? State their uses
Answer:

Halons arc halocarbons. They used as fire extinguishers

Question 9. Why is the tropospheric ozone harmful?
Answer:

Ozone gas present In the troposphere acts as a greenhouse gas.

Question 10. Mention the season and time of the day when London smog is generally observed.
Answer:

During winter, particularly after evening or early in the morning London smog is generally observed.

Question 11. Mention the season and time of the day when Los Angeles smog is generally observed
Answer:

During the mid-days of the summer season when the sun shines brightly this kind of smog is observed.

Question 12. Which region is most susceptible to the formation of photochemical smog?
Answer:

Photochemical smog is mostly observed in big cities, where there is considerable vehicular traffic on the roads throughout the whole day and night.

Question 13. Why is photochemical smog called Los Angeles smog?
Answer:

This type of smog was first discovered in the city of Los Angeles in America in the year 1950. So it is called Los Angeles smog.

Question 14. ‘There is “a ‘ tendency of environmental degradation of Tajmahal Explain
Answer:

SO₂ released from the industries situated around Tajmahal reacts photochemically with atmospheric O₂ and water vapour to form H₂SO₄. The H₂SO₄ hence produced reacts with white marble and damages it

Question 15. Give two examples of chlorinated organic pesticides.
Answer:

p, p’ -dichlorodiphenyltrichloroethane (DDT) and benzene hexachloride (BHC)

Question 16. What is loam soil?
Answer:

The soil containing almost equal amounts of sand, silt and clay along with humus, 34% of air and 64% of water is called loam soil

Question 17. Give two examples of each insecticide and herbicide
Answer:

Insecticide: DDT, BHC

Herbicide: 2,4-dichloro phenoxy acetic acid, dioxin

Question 18.   Write one effect of the depletion of the ozone layer and one measure for the prevention of ozone layer depletion.
Answer:

We have to reduce the use of compounds made by CFCs and halons

Question 19. Explain tropospheric pollution in 100 words.
Answer:

Tropospheric pollution occurs due to the presence of undesirable poisonous gases and solid particles in the air.

Question 20. What is anoxia or asphyxiation?
Answer:

Acute oxygen starvation in the body due to poisoning by carbon monoxide is called anoxia or asphyxiation.

Question 21. What is humification
Answer:

The process of decomposition of organic matter (roots, leaves etc.) in the soil by microorganisms to produce humus is called humification.

Question 22. Why does the population of fish get hindered by clouds? thermally polluted water
Answer:

Thermal pollution increases the temperature which in turn decreases the DO level of the water. Thus, it affects the fish badly and their growth gets retarded

Question 23.  Name four natural sources of air pollution.
Answer:

Volcanic eruptions, forest fires, lightning, decomposition of dead plant and animal bodies in marshyland.