UPSC Prelims 2010 · General Studies
Question 38: Environment and Ecology
Consider the following :
- 1.Oxides of Hydrogen
- 2.Oxides of Nitrogen
- 3.Oxides of Sulphur
Which of the above causes/cause acid rain ?
AnswerThe answer is (c).
Acid rain forms when sulphur dioxide and nitrogen oxides, released mainly by burning fossil fuels, dissolve in atmospheric water and form sulphuric and nitric acids. 'Oxides of hydrogen' is simply water (H2O), which is neutral and forms no acid. So only the oxides of nitrogen and sulphur are the culprits. Remember: SOx and NOx cause acid rain; CO2 only makes natural rain slightly acidic through carbonic acid.
- 1. Hydrogen oxide is water, which does not make acid rain.
- 2. Nitrogen oxides form nitric acid in the atmosphere.
- 3. Sulphur oxides form sulphuric acid in the atmosphere.
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: Hydrogen oxide is water, which does not make acid rain.
- Then, if you were sure statement 2 is correct, (b) goes: it leaves 2 out.
What you needed to know: Nitrogen oxides form nitric acid in the atmosphere.
Only (c) is left. You didn’t need statement 3.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
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) Oxides of hydrogen (water) are not acid-forming.
- (b) Oxides of nitrogen also cause acid rain.
- (c) Right: oxides of nitrogen and sulphur cause acid rain.
- (d) Oxides of hydrogen do not cause acid rain.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.