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CBSE Questions for Class 8 Chemistry Pollution Of Air And Water Quiz 11 - MCQExams.com
CBSE
Class 8 Chemistry
Pollution Of Air And Water
Quiz 11
As proved by many studies, the greenhouse effect is rapidly increasing because of increase in the concentration of carbon dioxide. In the given graph, the increase in carbon dioxide concentration is shown. What could be $$X$$ corresponding to it?
(i) Rate of photosynthesis in plants
(ii) $$pH$$ of the oceans
(iii) Water level of ocean
(iv) Average global temperature of earth
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(i) and (iii)
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(ii) and (iv)
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(ii) only
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(iv) only
Explanation
The recent phenomenon of global warming has been attributed primarily to increasing industrial $$CO_2$$ emissions into Earth's atmosphere. An estimated 3% of the $$CO_2$$ released by humans into the atmosphere dissolves into oceans, rivers and lakes which contributes to ocean acidification.
Hence, only (ii) is correct.
Smog is an example of:
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ice dispersed in air
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water dispersed in air
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smoke dispersed in air
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smoke and water dispersed in air
Explanation
Smog is made of smoke and fog (tiny water particles suspended in air). Smoke has oxides of nitrogen which combine with other air pollutants and fog, thus producing smog.
Read the given passage and select the correct option.
X
is a gas which occurs both in the earth's upper atmosphere (stratosphere) and at earth's ground level.
Y
are the substances which react with
X
and destroy the same. Beijing protocol was held to lay down steps to reduce
Y
released by developing and developed countries. Destruction of
X
can lead to diseases like cancer in humans.
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X prevent the harmful UV radiations from reaching the earth and also functions as green house gas.
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Cooling devices like air conditioners and refrigerators contribute to increase in Y in the earth's atmosphere.
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Maximum effect of Y occurs due to release of active chlorine which remains functional for a long time.
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All of these
Explanation
Here $$X$$ refers to oxygen gas which occurs in earth's upper atmosphere (stratosphere) as Ozone($$O_3$$) layer and at earth's ground level oxygen($$O_2$$) is present.
Here $$Y$$ refers to
chloroflurocarbons
(CFC)
which reacts with oxygen to destroy ozone layer.
Among the given statements all of them are correct as ozone prevents the harmful UV radiation reaching earth and CFC's are emitted by air conditioners and refrigerators, and also maximum effect of CFC'S occurs due to release of active chlorine which remains functional for a long time.
Hence, option $$D$$ is correct.
The green house gases, otherwise called radioactively active gases includes
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Carbon dioxide
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$$CH_{4}$$
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$$N_{2}O$$
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All of these
Which among the given is not a natural source of air pollution?
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Automobile exhausts
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Vegetation decay
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Forest fire
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Volcanic eruptions
Explanation
Automobile exhaustion is not a natural source of air pollution, it is man-made air pollution.
It is emitted as a result of the combustion of fuels such as natural gas, gasoline, petrol,bio-diesel etc.
It discharges a large amount of $$CO_2$$(carbon dioxide), $$NO$$, $$CO$$, $$ozone$$ etc.
Hence, the correct option is $$A$$.
Why are the environmental scientist worried about the effect of $$Q$$ on $$P$$?
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Because $$Q$$ emits sulphur oxides in air which cause acid rain over $$P$$
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Because $$Q$$ emits nitric acid in air which drops in the form of acid rain over $$P$$
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Because $$Q$$ emits soots particles in air which blackens $$P$$
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Both A and C
Carbon dioxide is called greenhouse gas because
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it traps heat
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it is used in photosynthesis
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it is exhaled during respiration
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its does not support combustion
Explanation
Carbon dioxide is an important gas as it is involved in the processes like respiration and photosynthesis. It is also used in fire extinguishers as it does not support combustion. But carbon- dioxide is called a greenhouse gas because it traps the heat coming from the sun. This helps in keeping the earth warm. But an increased amount of greenhouse gases will cause a greater amount of heat to be traped. This can be harmful to life on earth.
Carbon exists in the atmosphere in the form of:
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carbon monoxide only
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methane
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carbon dioxide
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coal
Explanation
In the atmosphere, carbon exists primarily in the form of carbon dioxide $$(CO_2)$$ and methane gas $$(CH_4)$$.
Which of the following is not a greenhouse gas?
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Carbon dioxide
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Sulphur dioxide
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Methane
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Nitrogen
Explanation
Nitrogen is not a greenhouse gas.
Greenhouse gases that occur both naturally and from human activities include water vapor, carbon dioxide, methane, nitrous oxide and ozone.
The Taj Mahal is being affected due to
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Air pollution
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Water pollution
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Radioactive pollution
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None of these
Explanation
Taj Mahal is being affected due to air pollution. Airborne particulate matter, made of black carbon, light- absorbing brown carbon and dust have a brown-tint that discolors the Taj Mahal's marble.
So the correct option is A.
Which of the following is major source of water pollution?
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Industrial waste
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Untreated sewage
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Agricultural waste
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All of the above
Explanation
When a harmful chemical substance, toxic waste, sewage, etc. gets mixed with water the water becomes polluted.
It has been found that many industries discharge harmful chemicals into rivers and streams causes water pollution.
Untreated sewage and agricultural waste also have similar discharges into water, which results in water pollution.
And these are major sources of water pollution.
Option $$D$$ is correct.
State true or false.
The greenhouse effect is only due to $$CO_2$$ gas.
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True
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False
Explanation
Greenhouse effect is mainly caused due to $$CO_2$$ gas but other gases like $$CH_4, H_2O$$(water vapour), nitrous oxide are also involved.
Hence, the given statement is wrong.
The gas released during anaerobic degradation of vegetation may lead to:
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Ozone hole
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Acid rain
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Corrosion of metals
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Global warming and cancer
Explanation
Methane $$(CH_{4})$$ gas is evolved due to anaerobic degradation of vegetation which causes global warming and cancer.
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