FRANK Solutions for Class 9 Chemistry Chapter 10 - Atmospheric Pollution

Chapter 10 - Atmospheric Pollution Exercise 158

Question 1

What is acid rain? Name two air pollutants that cause acid rain.

Solution 1

Acid rain is the rain that has an excessive amount of acid in it than that of normal. Two air pollutants that cause acid rain are-
(i) Oxides of nitrogen
(ii) Oxides of sulphur

Question 2

How is the ozone layer formed?

Solution 2

Question 3

Write a short note on "Greenhouse effect".

Solution 3

Greenhouse effect means the progressive warming up of the earth's surface due to the blanketing effect of man made carbon dioxide in the atmosphere. Greenhouse is a glasshouse with plants inside and  which allows short wave, incoming solar radiation to come in but does not allow the long wave,i.e. outgoing  infrared radiation to escape from inside the structure. Some of the gases in the earth's atmosphere act like the glass in a greenhouse.They trap sun's heat and keep the surface of the earth warm. Carbon dioxide and water vapour act as a greenhouse.

Question 4

Explain global warming.

Solution 4

Global warming is rise in the average global earth temperature . An increase in the average temperature of the earth's atmosphere due to greenhouse effect  which can have far reaching effects on the climate and consequently on the key life, support systems of the planet, and this phenomenon is called global warming.

Question 5

Draw a diagram to show greenhouse effect.

Solution 5

Question 6

What are the effects on environment by global warming?

Solution 6

(i) The warmer climate is changing the patterns of rainfall and snowfall.
(ii) It causes increase in the frequency and severity of drought and flood also.
(iii) It  is affecting our resources like water,forests  and different ecological systems.
(iv) It also cause frequent natural disasters like cyclones, storms and hurricanes,floods and droughts.
(v) The global warming is damaging various ecosystems like mangrove-swamps , coral reefs and coastal lagoons, etc. due to various reasons like reduction in pH of oceanic water and increasing deposits of acids.
(vi) It is damaging the world biodiversity. Vast varieties of birds, reptiles, insects, bacteria, fungi, rodents etc.have vanished out due to these effects.

Question 7

What is ozone hole?

Solution 7

It has been found that in every southern spring(September-October) 50-95 %  of stratospheric ozone is destroyed at a height of 15-24 kms above 'Antarctica' creating pockets which have been described as ozone hole.

Question 8

What are the adverse effects of ozone layer depletion?

Solution 8

The adverse effects of ozone layer depletion are-
(i) UV radiation causes sun-eye diseases (cataract), skin diseases, skin cancer and damage to immune system in our body.
(ii) It damages plants and causes reduction in crop productivity.
(iii) It damages embryos of fish, shrimps, crabs and amphibians.
(iv) UV radiation damage fabrics, pipes, paints and other non-living materials on this earth.
(v) It contributes in the global warming. If the ozone depletion continues, the temperature around the world may rise at faster rate and to a large extent.

Question 9

How greenhouse effect is useful for the existence of life on the earth?

Solution 9

Natural greenhouse effect is a process of thermal blanketing of the earth which maintains its temperature to sustain life on it. Without greenhouse effect, the climate of the earth would be too cold for most of the life to survive.

Question 10

How global warming is connected to greenhouse effects?

Solution 10

The effect of warming and insulation of the earth caused due to some heat trapping gases accumulated in the atmosphere after their emission from the earth surface is called as greenhouse effect. Due to this there is rise in the average global earth temperature called global warming.

Question 11

How does the ozone layer protect life on this planet?

Solution 11

When an ozone molecule is hit by UV wavelengths, it absorbs the radiant energy and photo dissociates into O₂ and O giving off heat. Thus, keeps the UV radiation from reaching the earth's surface and also causes a temperature inversion in the stratosphere that helps to maintain relatively stable climatic conditions on and near the ground.

Question 12

What is the affect of acid rain on forests?

Solution 12

Acid rain is responsible for retarding forest's growth and other vegetation. Acid rain makes the soil acidic and adversely affects the plants.

Question 13

Give sources of major greenhouse gases.

Solution 13

Sources of major greenhouse gases are-
(i) Natural sources
(ii) Fossil fuel combustion (coal, oil, natural gas)
(iii) Biomass burning and garbage landfills
(iv) Coal mines and natural gas leaks
(v) Paddy fields, swamps and tundra.

Question 14

How is acid rain formed? Explain.

Solution 14

70% of acid rain is due to sulphur dioxide. Oxides of sulphur and nitrogen released into atmosphere from number of sources.These oxides of nitrogen gets converted into nitrogen dioxide(NO₂) which reacts with water to form nitric acid.Similarly, sulphur dioxide reacts with atmospheric oxygen to form sulphur trioxide which with water forms sulphuric acid.These come down on earth as acid rain.

Question 15

What measures can be taken to reduce acid rain?

Solution 15

Acid rain can be reducd by-
(i) There should be reduction in fossil fuel combustion.
(ii) Use of alternate cleaner energy sources should be encouraged. Eg-nuclear power, hydro power, wind energy, solar energy etc.
(iii) Air filters and scrubbers are fitted in tall industrial chimneys to control air pollution.
(iv) Catalytic converters in vehicle reduce nitrogen oxide emissions from automobiles.

Question 16

What are the impact of acid rain on the environment?

Solution 16

Acid rain cause extensive damage to the environment.
(i) Vegetation - The acid rain makes the soil acidic. This adversely affects the plants and animals. This damages leaves of plants and trees. This is responsible for retarding forests and other vegetation.
(ii) Fertility of soil - The activity of symbiotic nitrogen fixing bacteria present in the nodules of leguminous family is inhibited. This is responsible for destroying or reducing the fertility of the soil.
(iii) Water bodies - Acid rain renders the river, lakes or even ocean water acidic, there by adversely affecting marine animals. Changes in pH affect the reproduction and survival of many species of fish and other animals.
(iv) Buildings and monuments-Acid rain cause extensive damage to the buildings and monuments made from marbles, limestone, slate and mortar

(v) Ecological balance - Acid rain is responsible for wiping out many bacterial and blue green algae, so disrupting the whole ecological balance.
(vi) Human health - Acid rain has been found to be dangerous to human health. Acidic conditions can affect human nervous, respiratory and digestive systems.

Question 17

Define air pollution.

Solution 17

Air pollution is a harmful change in the natural air quality. It includes all physical, chemical and biological agents that modify the natural characteristics of the atmosphere.

Question 18

What is ozone?

Solution 18

Ozone is an allotrope of oxygen. It has three oxygen atoms and its molecular formula is O₃.It is an unstable blue gas having pungent odour found in troposphere. It is used as a powerful oxidant, bleach and water purifier.

Question 19

Name the gases causing ozone depletion?

Solution 19

The gases causing ozone depletion are-
(i) Chlorofluoro carbons(CFCs or freons)
(ii) Methane
(iii) Nitrous oxides
(iv) Carbon tetrachloride
(v) Methyl bromide(a soil fumigant and insecticide)
(vi) Aircraft emission
(vii) n-propyl bromide and Halon-1202

Question 20

Name the greenhouse gases.

Solution 20

Greenhouse gases are-
(i) Water vapour(H₂O)
(ii) Carbon dioxide(CO₂)
(iii) Methane(CH₄)
(iv) Oxides of nitrogen(NOx)