Section Name Topic Name

14 Environmental Chemistry

14.1 Environmental Pollution

14.2 Atmospheric Pollution

14.3 Water Pollution

14.4 Soil Pollution

14.5 Industrial Waste

14.6 Strategies to control Environmental Pollution

14.7 Green Chemistry

Question 1. Define environmental chemistry?

Answer: Environmental Chemistry is the branch of science which deals with
the chemical changes in the environment. It includes our surroundings such
as air, water, soil, forest etc.

Question 2. Explain the tropospheric pollution in 100 words?

Answer: Tropospheric pollution occurs due to the presence of undesirable
substance in air. These may be the solid or gaseous pollutants.

 Gaseous Air Pollutants: These are oxides of sulphur, nitrogen and

carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.

 Particulate Pollutants: These are dust, mist, fumes, and smog etc.

uestion 3. Carbon monoxide gas is more dangerous than carbon

dioxide gas. Why?
Answer: Carbon monoxide combines with haemoglobin to form a very stable
compound known as carboxyhaemoglobin when its concentration in blood
reaches 3-4%, the oxygen carrying capacity of the blood is greatly reduced.
This results into headache, nervousness and sometimes death of the person.
On the other hand CO2 does not combine with haemoglobin and hence is less
harmful than CO.

Question 4. Which gases are responsible for greenhouse effect? List

some of them.
Answer: CO2 is mainly responsible for greenhouse effect. Other greenhouse
gases are methane, nitrous oxide, water vapours, CFCs and Ozone.

Question 5. Statues and monuments in India are affected by acid

rain. How?
Answer: This is mainly due to the large number of industries and power
plants in the nearby areas. Acid rain has vapours of sulphuric acid dissolved
in it. When it comes in contact with various statues or monuments, the acid
reacts chemically with calcium carbonate.
CaCO3 + H2SO4 ——–> CaSO4 + H2O + CO2

Question 6. What is smog? How is classical smog different from

photochemical smog?
Answer: The word smog is a combination of smoke and fog. It is a type of air
pollution that occurs in many cities throughout the world. Classical smog
occurs in cool humid climate. It is also called as reducing smog.Whereas
photochemical smog occurs in warm and dry sunny climate. It has high
concentration of oxidising agents and therefore, it is also called as oxidising
smog.

Question 7. Write down the reactions involved during the formation

of photochemical smog.
Answer: Mechanism of formation of photochemical smog:

Question 8. What are the harmful effects of photochemical smog

and how can they be controlled?
Answer: Harmful effects of photochemical smog:

 Their’high concentration causes headache, chest pain and dryness of

the throat.
  Ozone and PAN act as powerful eye irritants.

 Photochemical smog leads to cracking of rubber and extensive damage

to plant life.

 It causes corrosion of metals, stones, building materials, and painted

surface etc.

Control:

 Use of catalytic converter in automobiles prevents the release of

nitrogen dioxide and hydrocarbons to the atmosphere.

 Pinus, juniparus, quercus, pyrus etc. can metabolise nitrogen dioxide

thus their plantation could help to some extent.

Question 9. What are the reactions involved for ozone layer

depletion in the stratosphere?
Answer: The reaction can be shown as follows:
CF2Cl2(g) + UV ——-> Cl(g) + CF2Cl(g)
Cl(g) + O3(g) ———-> ClO (g) + O2(g)
ClO(g) + O(g) ———> Cl + O2(g)

Question 10. What do you mean by ozone hole? What are its
consequences?
Answer: Depletion of ozone layer creates some sort of holes in the blanket
of ozone which
surround us, this is known as ozone hole.

 With the depletion of the ozone layer, UV radiation filters into the
troposphere which leads to aging of skin, cataract, sunburn, skin
cancer etc.

 By killing many of the phytoplanktons, it can damage the fish

productivity.

 Evaporation rate increases through the surface and stomata of leaves

which can decrease the moisture content of the soil.

Question 11. What are the major causes of water pollution? Explain.
Answer: Causes of water pollution:

 Pathogens: Pathogens include bacteria and other microorganisms

that enter water from domestic sewage and animal excreta.
Human excreta contain bacteria such as Escherichia coli and
 Streptococcus faecalis ,
which cause gastrointestinal diseases.

 Organic wastes: Organic wastes when added to water, as these are

biodegradable, bacteria decomposes organic matter and consume
dissolved oxygen in water. When the concentration of dissolved oxygen
of water is below 6 ppm, the growth of fish gets inhibited. Breakdown
of the organic wastes by anaerobic bacteria produces chemicals that
have a foul smell and are harmful to human health.

 Chemical pollutants: Some inorganic chemicals as an industrial

wastes dissolve in water like cadmium, mercury nickel etc. These
metals are dangerous to humans and other animals. These metals can
damage kidneys and central nervous system,lever etc. Petroleum
products pollute many sources of water.

Question 12. What do you mean by Biochemical Oxygen Demand

(BOD)?
Answer: The amount of oxygen required by bacteria to breakdown the
organic matter present in a certain volume of a sample of water is called
Biochemical Oxygen Demand (BOD).

Question 13. What are pesticides and herbicides? Explain giving

examples.
Answer: Pesticides are the chemical compounds used in agriculture to
control the damages caused by insects, rodents, weeds and various crop
diseases.
Example: Aldrin, Dilldrin, B.H.C etc.
Herbicides: These are the chemicals used to control weeds.
Example: Triazines.

Question 14. What do you mean by green chemistry? How will it

help in decreasing environmental pollution ?
Answer: Green chemistry is a way of thinking and is about utilising the
existing knowledge and principles of chemistry and other sciences to reduce
the adverse effect of pollution.
For example:

 Automobile engines have been fitted with catalytic converters which

prevent the release of the vapours of hydrocarbons and oxides of
nitrogen into acrolein and peroxyacetyl nitrate.
  CO2 has replaced CFCs as blowing agents in the manufacture of
polystyrene foam sheets.

Question 15. What would have happened if the greenhouse gases

were totally missing in the earth’s atmosphere? Discuss.
Answer: The solar energy radiated back from the earth surface is absorbed
by the green house gases. (CO2, CH4, O3, CFCs) are present near the earth’s
surface.
They heat up the atmosphere near the earth’s surface and keep it warm. As
a result of these, there is growth of vegetation which supports the life. In the
absence of this effect, there will be no life of both plant and animal on the
surface of the earth.

Question 16. A large number offish 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: Excessive phytoplankton (organic pollutants such as leaves, grass
trash etc.) present in water are biodegradable. Bacteria decomposes these
organic matters in water. During this process when large number of bacteria
decomposes these organic matters, they-consume the dissolved oxygen in
water. When the level of dissolved oxygen falls below 6 ppm the fish cannot
survive.

Question 17. How can domestic waste be used as manure?

Answer: Domestic waste consists of biodegradable waste which can be
converted into manure by suitable method.

Question 18. 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 of wastes for a good produce.
Answer: The compost producing pit should be kept covered so that flies
cannot make entry into it and bad odour is minimized.
The waste materials which are non-biodegradable like glasses, plastic bags,
polybags, must be handed over to the vendors who can send them to the
recycling plants.

MORE QUESTIONS SOLVED

NCERT Solutions for Class 11 Chemistry Chapter 14 Very Short Answer Type
Questions

Question 1. What do you mean by primary and secondary pollutants

of the air?
Answer: Primary pollutants are those which after their formation remains as
it was before e.g., NO. Secondary pollutants are formed as a reaction with
primary pollutants e.g., PAN (peroxyacyl nitrates).

Question 2. What is the name of the compound formed when CO

combines with blood?
Answer: Carboxyhaemoglobin.

Question 3. How are NO and NO2 formed in the atmosphere?

Answer: NO is formed due to the reaction between N2 and O2 during
lightning or by the combustion of fossil fuels.NO is oxidised to form NO 2.

Question 4. What is chlorosis?

Answer: Slowdown of process of formation of chlorophyll in plants with the
presence of SO2 is called chlorosis.

Question 5. Which zone is known as ozonosphere?

Answer: Stratosphere.

Question 6. Which main gases is responsible for damage in ozone

layer?
Answer: NO and CFCs

Question 7. What is the nature of classical smog?

Answer: Reducing.

Question 8. Name the acids which are responsible for acid rain?
Answer: H2SO4, HNO3 and HCl.

Question 9. What is BOD?

Answer: The amount of oxygen consumed by micro organism in
decomposing organic wastes of sewage water is called BOD (Biochemical
Oxygen Demand).

Question 10. What do you mean by viable and non-viable

particulates?
Answer: Viable particulates are microorganisms like bacteria, fungi,
moulds, algae etc. Non- viable particulates are formed by the disintegration
of bigger size particles or by the condensation of water vapour, e.g., mist,
smoke, fume and dust.

Question 11. What is siltation?

Answer: Mixing of soil or rock particles in water is called siltation.
Question 12. What is the composition of London Smog?
Answer: London Smog consists H2SO4 deposited on the particulates
suspended in the atmosphere.

Question 13. List out the gases which are considered as major
source of air pollution.
Answer: Carbon monoxide (CO), sulphur dioxide (SO2) and oxides of
nitrogen (NO2).

Question 14. Why is acid rain considered as threat to Taj Mahal ?

Answer: Acids present in acid rain can react with marble (CaCO 3) and
damage the monument.

Question 15. Give one example of organic herbicide.

Answer: Triazines.

Question 16. What are pesticides ?

Answer: Pesticides are the substances used to kill unwanted pests. For
example, DDT.

Question 17. What is PAN stands for?

Answer: It is peroxyacetyl nitrate.

Question 18. Give the examples of insecticides.

Answer: DDT, BHC.

Question 19. Which gas was mainly responsible for Bhopal gas
tragedy?
Answer: Methyl isocyanate.

Question 20. What is meant by polar vortex?

Answer: A tight whirlpool of wind formed in the stratosphere which
surrounds Antarctica is called polar vortex.

Question 21. What should be the tolerable limit of F ions in drinking

water?
Answer: 1 ppm or 1 mg dm-3.

NCERT Solutions for Class 11 Chemistry Chapter 14 Short Answer Questions

Question 1. How did carbon monoxide act as a poison for human

beings?
Answer: Carbon monoxide is poisonous because it combines with
hemoglobin of R.B.C. to form carboxyhemoglobin as.
It inhibits the transport of oxygen to different parts of the body. Thus the
body becomes oxygen-starved.

Question 2. What is ‘Acid Rain’? How is it harmful to the

environment?
Answer: Acid rain is the rain water mixed with small amount of sulphuric
acid, nitric acid along with hydrochloric acid which are formed from the
oxides of sulphur and nitrogen present in air as pollutants. It has a pH of 4-5.
Harmful effects of Acid Rain

 It is toxic to vegetation and aquatic life.

 It damages buildings and statues. Taj Mahal has been damaged by acid
rain.

 Acid rain corrodes water conducting pipes resulting in the leaching of

heavy metals such as iron, lead, etc., to the drinking water.

Question 3. What is photochemical smog? What are its effects? How

can it be controlled?
Answer: This is a type of smog formed in warm, dry and sunny climate.
They are formed when sunlight is absorbed by SO 2, oxides of nitrogen and
hydrocarbons.
They act as oxidising agents.
Effects of photochemical smog

 They produce irritation in the eyes and also in respiratory system.

 They can damage many materials such as metals, stones, building

materials etc.

 NO2 present gives a brown colour to the photochemical smog which

reduces visibility.

 It is harmful to fabrics, crops and ornamental plants.

Control of photochemical smog

 By using catalytic converters in automobiles.

 By spraying certain compounds into atmosphere which generate free

radicals that can easily combine with the free radicals that initiate the
reaction forming toxic compounds of photochemical smog.

 Certain plants such as pinus, juniparus, pyrus could be helpul in this

matter.
Question 4. What do you mean by greenhouse effect? What is the
role of CO2 in the greenhouse effect?
Answer: It is the phenomenon in which earth’s atmosphere traps the heat
from the sun and prevents it from escaping in outer space. Gases such as
CO2, methane, ozone, CFCs are believed to be responsible for this effect.Heat
from the sun after being absorbed by the earth is absorbed by CO 2 and then
radiated back to the earth. Thus making the environment of the earth warm.

Question 5. (a) Define eutrophication and pneumoconiosis.

(b) Write difference between photochemical and classical smog.
Answer: (a) Eutrophication: When the growth of algaes increases in the
surface of water, dissolved oxygen in water is reduced. This phenomenon is
known as eutrophication. (Due to this growth of fish gets inhibited).
Pneumoconiosis: It is a disease which irritates lungs. It causes scarring or
fibrosis of the lung.
(b)

Photochemical smog Classical smog

(i) It is formed as a result of photochemical (i) It is formed due to condensation of SO,

decomposition of nitrogen dioxide and vapours on particles of carbon in cold
chemical reactions involving hydrocarbons. climate.
(ii) It takes place during dry warm season in (ii) It is generally formed during winter wh
presence of sunlight. there is severe cold.
(iii) It is oxidising in nature. (iii) It is reducing in nature.

NCERT Solutions for Class 11 Chemistry Chapter 14 Multiple Choice

Questions

Question 1. Which of the following acid is most abundant in acid

rain?
(a) HCl (b) HNO3 (c) H2SO4 (d)Organic acid
Question 2. Which of the following causes less pollution?
(a) NOx (b) SOx (c) CO2 (d) CxHy
Question 3. Besides CO2, the other greenhouse gas is
(a) Ar (b) N2 (C) O2 (d) CH4
Question 4. BOD is a measure of
(a) Organic pollutant in water (b) Inorganic pollutant in water
(c) Particulate matter in water (d) All of the above
Question 5. The gas which reacts with hemoglobin in blood is
(a) CO (b) SO2 (c) CO2 (d) NO2
Question 6. Ozone depletion is mainly due to
(a) HCFs (b) CFCs (c) CH3Br (d)all of the above
Question 7. The pollutant released in Bhopal gas tragedy was
(a) Ammonia (b) Mustard gas (c) Nitrous oxide (d) Methyl isocyanate
Question 8. Which of the following will increase the BOD of water
supply?
(a) O3 (b) C2H5OH (C) H2O (d) CO2
Answer: 1.(c) 2. (c) 3. (d) 4. (a) 5. (a) 6.(b) 7. (d) 8. (c)

NCERT Solutions for Class 11 Chemistry Chapter 14 Hots Questions

Question 1. What is meant by PCBs?

Answer: PCBs are polychlorinated biphenyls. They are contaminants of
water. They are used as fluids in transformers and capacitors.

Question 2. What is the compound formed when CO combines with

blood?
Answer: When CO combines with blood, the following reaction occurs
forming carboxyhaemoglobin:-
HB + CO —> (HBCO) Carboxyhaemoglobin

Question 3. Give three examples in which green chemistry has been

applied.
Answer:

 In dry-cleaning, use of liquefied CO2 in place of tetrachloroethene (Cl2C

= CCl2).

 In bleaching of paper using H2O2 in place of chlorine.

 In the manufacture of chemicals like ethanal using environment-

friendly chemicals and conditions.

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