UPSC Prelims 2022 · Question 100 of 98

UPSC Prelims 2022 question on Acid Rain Causes

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?

  1. 1, 2 and 3
  2. 2 and 4 only
  3. 4 only
  4. 1, 3 and 4
Show answer

Answer: B. 2 and 4 only

Analysis

Acid rain results when sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents. The SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.

Causes of acid rain: Nitrogen oxide (2) and Sulphur dioxide (4) → Option (b) 2 and 4 only.

Statement by statement

Statement 1 – Carbon monoxide: NOT a cause of acid rain. CO does not directly form acid rain.

Statement 2 – Nitrogen oxide: CORRECT cause of acid rain. NOX reacts with water to form nitric acid.

Statement 3 – Ozone: NOT a primary cause of acid rain. Ozone is a secondary pollutant and not directly responsible for acid rain formation.

Statement 4 – Sulphur dioxide: CORRECT cause of acid rain. SO2 reacts with water to form sulfuric acid.

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