Chapter 10: Environmental ChemistryMCQs with Answers
All 24 MCQs of 9th Class Chemistry Chapter 10, Environmental Chemistry, with answers and the reason each option is right or wrong: the 10 textbook exercise MCQs plus 14 more board-style MCQs. Punjab Board new syllabus.
Try each one first: tap an option to check it, then read the reasoning and why the others are wrong.
A note about the questions
The wording follows published solved exercises and every answer was re-checked by hand, so the wording or the order of options may differ slightly from your print.
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Set A: Textbook exercise 10 MCQs
The multiple-choice questions at the end of Chapter 10 in your book, in the book's option order.
Q10.1Greenhouse Effect and Global Warming
Which gases are responsible for the greenhouse effect?
Answer(c) CO₂, CH₄
Step by step
Greenhouse gases: CO₂, CH₄, H₂O.
SO₂ and NO₂ are acid-rain gases.
Why the others are wrong
(a) these cause acid rain.
(b) CO is toxic but not a main greenhouse gas.
(d) the main gases of air do not absorb heat radiation.
Remember
Greenhouse = carbon gases: CO₂ and CH₄.
Q10.2Air Pollutants and Sources
Indicate the source of sulphur which is responsible for the presence of oxides of sulphur in the atmosphere.
Answer(d) Combustion of fossil fuels
Step by step
Coal and oil contain sulphur compounds.
Burning → SO₂.
Why the others are wrong
(a) that gives methane.
(b) that gives methane.
(c) smog contains ozone and NOₓ; it is not a source of sulphur.
Remember
Sulphur is in the fuel.
Q10.3Strategies to Reduce Pollution
Concentration of which gas in the atmosphere is decreased by photosynthesis in plants?
Answer(c) Carbon dioxide
Step by step
CO₂ used up; O₂ given out.
Why the others are wrong
(a) oxygen increases.
(b) not used.
(d) water comes from the soil, and plants give out water vapour.
Remember
Plants breathe in CO₂.
Q10.4Strategies to Reduce Pollution
Which substance remains unaffected in the catalytic converter fixed in the exhaust of automobiles?
Answer(a) CO₂
Step by step
2CO + O₂ → 2CO₂.
2NOₓ → N₂ + xO₂.
Why the others are wrong
(b) oxidised to CO₂.
(c) reduced to N₂.
(d) reduced to N₂.
Remember
CO₂ is what comes out, not what is removed.
Q10.5Air Quality and Protection
People of which age groups are most affected by air pollution?
Answer(d) Both children and aged people
Step by step
High-risk: under 18 and over 65.
Why the others are wrong
(a) the least sensitive group.
(b) Wrong.
(c) only half the answer.
Remember
The very young and the old.
Q10.6Acid Rain
In which area is there a greater possibility of acid rain?
Answer(c) Around industrial areas
Step by step
Most SO₂ and NOₓ come from industry and power stations.
Why the others are wrong
(a) little fuel burnt.
(b) partly true, but industry is the main source.
(d) water bodies suffer from it but do not cause it.
Remember
Factories make the acid gases.
Q10.7Air Pollutants and Sources
Why is smog not felt in summer?
Answer(a) Because fog is not present in summer
Step by step
Smog = smoke + fog.
No fog in summer → no smog.
Why the others are wrong
(b) partly true, warm air does carry smoke upwards and away, but the book's reason is the absence of fog.
(c) they would mix if fog were present.
(d) fuel is burnt all year round.
Remember
No fog, no smog.
Q10.8Strategies to Reduce Pollution
Which catalyst is used in the catalytic converters fixed in the exhaust systems of automobiles?
Answer(c) Pt, Pd and Rh
Step by step
Converter: Pt, Pd, Rh.
Why the others are wrong
(a) margarine.
(b) Wrong.
(d) used to remove SO₂ from flue gas.
Remember
Precious metals in the exhaust.
Q10.9Air Pollutants and Sources
Which components are essential for the formation of photochemical smog?
