UPSC Prelims 2013 · GS Paper I
Question 30: Environment and Ecology
Acid rain is caused by the pollution of environment by
AnswerUPSC’s answer is (d).
Acid rain forms when sulphur dioxide and oxides of nitrogen, released by burning coal and oil and by vehicles, react with water, oxygen and other chemicals in the air to form sulphuric and nitric acids. These fall as rain, snow or dust. Carbon dioxide makes rainwater only mildly acidic, and carbon monoxide and ozone are not the cause.
Why each option is right or wrong
- (a) Wrong. Carbon dioxide and nitrogen are not the cause of acid rain.
- (b) Wrong. Neither carbon monoxide nor carbon dioxide forms strong acids in the air.
- (c) Wrong. Ozone and carbon dioxide are not the main acid-rain gases.
- (d) Correct. Oxides of sulphur and nitrogen are the cause.
Worth knowing: Strictly, acid rain comes from nitric oxide and nitrogen dioxide rather than nitrous oxide (N2O); UPSC treated option (d) as sulphur and nitrogen oxides.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.