UPSC Prelims 2003 Q106: Environment & Ecology – Pollution & Waste Management
Assertion (A): Coal - based thermal power stations contribute to acid rain.
Reason (R): Oxides of carbon are emitted when the coal burns.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is NOT the correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (b) Both A and R are individually true but R is NOT the correct explanation of A
Explanation
Coal-based power stations and acid rain
| Part | Verdict |
|---|---|
| A. Coal-based thermal power stations contribute to acid rain | True — through sulphur and nitrogen oxides |
| R. Oxides of carbon are emitted when coal burns | True — but they are not the cause of acid rain |
Both statements are true, but R does not explain A, because acid rain is caused by oxides of sulphur and nitrogen, not by oxides of carbon.
Answer: (b) Both A and R are true but R does not explain A.
Why each option is right or wrong
- (a) Incorrect. R does not explain A, since carbon oxides do not cause acid rain.
- (b) CORRECT. A is true because of SO2 and NOx, and R is true but is not the cause of acid rain.
- (c) Incorrect. R is also true, so this code is wrong.
- (d) Incorrect. A is true, so this code is wrong.
Key point
Acid rain: SO2 to H2SO4, NOx to HNO3; CO2 gives only weak carbonic acid.
Remember
Acid rain from thermal plants is caused by oxides of sulphur and nitrogen.
Common mistakes
- Treating CO2 as the main acid rain gas.
- Forgetting the sulphur content in coal.
- Mixing up acid rain with global warming issues.
Exam tip
The pollutants behind acid rain are SO2 and NOx.
Sources
- NCERT Class XI Chemistry — Environmental Chemistry (acid rain)
- Encyclopaedia Britannica — acid rain