UPSC Prelims 2011 · GS Paper I
Question 2: Environment and Ecology
Consider the following :
- 1.Carbon dioxide
- 2.Oxides of Nitrogen
- 3.Oxides of Sulphur
Which of the above is/are the emission/emissions from coal combustion at thermal power plants ?
AnswerThe answer is (d).
Burning coal in a thermal power plant releases carbon dioxide from the carbon in the fuel, oxides of sulphur from the sulphur present in coal, and oxides of nitrogen formed from the nitrogen in the fuel and in the air at high furnace temperatures. It also emits fly ash, particulates and traces of mercury. Sulphur and nitrogen oxides cause acid rain, while carbon dioxide is the main greenhouse gas. All three listed gases are emissions.
- 1. Carbon in coal burns to carbon dioxide.
- 2. Nitrogen in fuel and air forms oxides of nitrogen at furnace temperatures.
- 3. Sulphur in coal burns to oxides of sulphur.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Carbon in coal burns to carbon dioxide.
- Then, if you were sure statement 2 is correct, (a) and (c) go: each of them leaves 2 out.
What you needed to know: Nitrogen in fuel and air forms oxides of nitrogen at furnace temperatures.
Only (d) 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) Carbon dioxide is emitted, but it is not the only emission.
- (b) Leaves out carbon dioxide, the main product of burning coal.
- (c) Leaves out oxides of nitrogen, which form in the hot furnace.
- (d) Right: all three gases come out of coal combustion.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.