NCERT Class 11 Chemistry Chapter 14 Environmental Chemistry Long Answer Questions

NCERT Class 11 Chemistry Chapter 14 Environmental Chemistry Long Question And Answers

Question 1. What do you mean by reducing smog and oxidising smog?
Answer:

• Ordinary smog contains sulphur dioxide (SO₂), very fine carbon particles and some other reducing agents.
• As a result of this ordinary smog exhibits reducing property.
• So smog of this type is called reducing smog. Photochemical smog by the presence of oxidising substances such as ozone, NO₂ peroxyacyl nitrate etc. shows oxidising properties.
• As a result of this photochemical smog is sometimes called oxidising smog.

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Question 2. What is the Montreal Protocol?
Answer:

• Nowadays, the depletion of the ozone layer in the stratosphere by various greenhouse gases has been a matter of great concern to the scientists of the whole world.
• As a result of this, the decision to prohibit the use of the chief greenhouse gas i.e., chlorofluorocarbon (CFC) was adopted in 1993 in a convention of scientists, arranged in Montreal, Canada.
• This is known as the Montreal Protocol. India also signed this agreement

Question 3. What is the Bhopal gas tragedy? Mention the after-effects of the Bhopal gas tragedy.
Answer:

• Bhopal gas tragedy was a gas leak incident in India. This incident is considered the world’s worst industrial disaster.
• It occurred at the midnight of 2-3 December 1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh.
• Over 5,00,000 people were exposed to the poisonous methyl isocyanate (MIC) gas.
• Among those people, around 3000 people died from the immediate effect of the gas leakage.
• The initial effects of exposure were coughing, vomiting, severe eye irritation and suffocation.
• The people of the affected area, still suffering from the after-effects of the tragedy.

Question 4. In the stratosphere, ozone is useful, but in the troposphere, it is harmful to us— explain.
Answer:

The layer of ozone gas present in the stratosphere which extends from a height of 15 km to 75 km from the sea level of the earth’s surface is known as the ozone layer or ozonosphere.

• The harmful ultraviolet rays (UV rays) coming from the sun are mostly absorbed in the ozone layer because these rays are utilised in the production and dissociation of ozone gas.
• The absence of this ozone layer would allow the ultraviolet rays coming from the sun to reach the earth’s surface entirely.
• This would have heated the earth’s surface and the adjacent air to such an extent that the existence of the living world in land and water would have been jeopardised.
• But, ozone gas present in the troposphere acts as a greenhouse gas.
• Ozone gas contributes nearly 7-8% to the creation of the greenhouse effect.
• Due to greenhouse effects, the surface temperature of the earth will rise and this eventually will melt the polar caps accumulated in polar regions which will cause colossal devastation by tidal waves, cyclones, super cyclones.
• Thus ozone, in the stratosphere is useful but in the troposphere is harmful.

Question 5. The extensive depletion of the ozone layer occurs from September to October. Explain this phenomenon.
Answer:

In Antarctica, during the months (March to August) just before the advent of spring season (September-October), the temperature drops below -90°C.

• As a result, the water vapour in the atmosphere condenses to form polar stratospheric clouds.
• Different oxides of nitrogen which are floating in the atmosphere produce nitric acid (HNO₃) in contact with the crystals of ice in the cloud.
• In this condition, chlorine derived from the chlorofluorocarbon (CFC) compounds does not find any opportunity to become inert by reaction with the oxides of nitrogen because chlorine is not capable of reacting with the nitric acid.
• As a consequence of this phenomenon, during the few months from March to August (when the sky in Antarctica remains covered with darkness), chlorine keeps on accumulating in the stratosphere.
• Then, with the arrival of spring, the chlorine present in the atmosphere becomes very reactive in the presence of sunlight and triggers the process of breaking ozone (O₃) molecules in the ozone layer.
• Thus, extensive depletion of the ozone layer takes place from September to October.

Question 6. Name the greenhouse gases and mention their sources due to human activities.
Answer:

Question 7. What is an atomic power plant? What Is Chernobyl Disaster? What is the cause of this accident?
Answer:

The power plant produces electricity by the nuclear fission reaction of radioactive elements such as uranium. Plutonium etc. is called an atomic power plant.

Chornobyl is a city in Ukraine in the former Soviet Union. On the 26th of April 1986, the accident that occurred with horrifying consequences and destroyed the environment has remained alive in our memory as the Chornobyl disaster.

As a result of this tragic accident, the radioactive emission spread over an area of about 3000 sq km and nearly ten crores of people had to be rehabilitated. Uranium was used as fuel in the plant for the generation of electricity. On the day of the accident, due to the lack of proper safety measures, uranium fuel in the atomic reactor, being exceedingly heated, caused the explosion.

Question 8. Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?
Answer: 

The colourless, odourless carbon monoxide gas is severely harmful to human beings and animals. It has a greater affinity towards haemoglobin than that of oxygen. So, it readily displaces oxygen from oxyhaemoglobin (HbO₂) to form the more stable compound carboxyhaemoglobin (HbCO) to give a stable compound, carboxy haemoglobin.

HbO₂ + CO ⇌  HbCO + O₂

In blood, when the concentration of carboxy haemoglobin reaches 3-4%, the oxygen-carrying capacity of the blood is greatly reduced. In other words, the body becomes oxygen-starved. results in headache, nervousness, cardiovascular disorder, weak eye-sight etc., On the other hand, CO₂ does not combine with haemoglobin and hence is less harmful as a pollutant. CO₂. is mainly responsible for the greenhouse effect and global warming

Question 9. What are the harmful effects of photochemical smog, and how can they be controlled?
Answer:

Photochemical smog can be controlled in the given ways: 

By using efficient catalytic converters in automobiles, will check the release of both NO₂ and certain hydrocarbons known as primary precursors.

• This will automatically check the formation of secondary precursors. Such as Ozone and PAN.
• By spraying certain compounds into the atmosphere which will control hydrocarbons, NO₂, and PAN.
• Certain plants like pinus, Pyrus, Vitis Quercus etc., are capable of causing the metabolism of the oxides of nitrogen. Hence, their plantation could be helpful.

Question 10. What are herbicides? Explain giving
Answer:

Herbicides:

• These are the chemicals employed to control weeds. The common herbicides are sodium chlorate (NaClO₃) and sodium arsenite (Na₃AsO₃).
• These herbicides are no longer preferred because they are toxic towards mammals.
• At present, organic herbicides like triazines are used as weed controllers and have no adverse effect on human beings.

Question 11. A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping, but you find an abundance of phytoplankton. Suggest a reason for the fish kill.
Answer:

• The presence of excess phosphate and nitrate compounds increases the growth of phytoplankton (organic pollutants such as leaves, grass, trash etc.).
• A large population of bacteria decomposes this organic pollutant.
• During this process, they consume the dissolved oxygen of water, which is of course very much essential for the life of sea animals, particularly fish.
• When the level of dissolved oxygen falls below 6 ppm, the fish cannot survive.
• Hence, a large number of fish are found floating dead on the lake

Question 12. How can domestic waste be used as manure?
Answer:

• Domestic wastes consist of two types of materials, biodegradable such as leaves, rotten food, vegetable refuse etc., and non-biodegradable portion which consists of plastic, glass, metal scrap etc.
• The biodegradable waste should be deposited in the landfills.
• Then this waste gets converted into time.

Question 13.  For your agricultural field or garden, you have developed a compost-producing pit.  Discuss the process in the light of bad odour, flies and recycling.
Answer:

• The compost-producing pit should be developed at a suitable place to protect ourselves from bad odour and flies.
• It should be covered properly to prevent the entry of flies and the emission of foul odour.
• The waste materials like plastics, glass, newspapers etc must be handed over to the vendors.
• These are finally sent to the recycling industry without creating a pollution problem.