UPSC Prelims 2022 · GS Paper I
Question 100: Environment and Ecology
Consider the following :
- 1.Carbon monoxide
- 2.Nitrogen oxide
- 3.Ozone
- 4.Sulphur dioxide
Excess of which of the above in the environment is/are cause(s) of acid rain ?
AnswerUPSC’s answer is (b).
Acid rain forms when sulphur dioxide and nitrogen oxides in the air react with water, oxygen and other chemicals to form sulphuric and nitric acids. Burning coal and oil and vehicle exhaust are the main sources. Carbon monoxide is a toxic gas that does not form acids this way, and ozone is a pollutant and oxidant, not a cause of acid rain.
- 1. Carbon monoxide does not form acids in the atmosphere.
- 2. Nitrogen oxides form nitric acid.
- 3. Ozone is an oxidant pollutant, not a cause of acid rain.
- 4. Sulphur dioxide forms sulphuric acid.
How you could have got this
- If you were sure statement 1 is not correct, (a) and (d) go: each of them includes 1.
What you needed to know: Carbon monoxide does not form acids in the atmosphere.
- Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: Nitrogen oxides form nitric acid.
Only (b) is left. You didn’t need statements 3 or 4.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Wrong. Carbon monoxide and ozone do not cause acid rain.
- (b) Correct. Nitrogen oxides and sulphur dioxide form acids.
- (c) Wrong. Nitrogen oxides also contribute.
- (d) Wrong. Carbon monoxide and ozone do not cause acid rain.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper I, Series A. The paper on upsc.gov.in.