Question 79 from UPSC CSE 2022 - Environme nt

Question

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?

IASCODEX · Accepted Answer

Correct Option: B. 2 and 4 only

Strategy: Identify the primary causative agents of acid rain.
*   Recall that acid rain results from acidic oxides, specifically sulfur dioxide (SO2) and nitrogen oxides (NOx), which form sulfuric and nitric acid.
*   Eliminate compounds like carbon monoxide and ozone, as they do not significantly contribute to acid rain.

Key Info: Acid rain is primarily caused by atmospheric deposition of acids formed from sulfur dioxide (SO2) and nitrogen oxides (NOx). These gases are released mainly by the combustion of fossil fuels in industries, power plants, and vehicles. SO2 transforms into sulfuric acid and NOx into nitric acid upon reacting with atmospheric moisture and oxygen.

### Key Compounds and their Role

*   **Carbon monoxide (CO)**: Not acidic; does not contribute to acid rain. It is a toxic gas involved in smog formation and health hazards.
*   **Nitrogen oxides (NOx)**: Primarily NO and NO2, react with water and oxygen to form nitric acid (HNO3), a major contributor to acid rain.
*   **Ozone (O3)**: A secondary pollutant not involved in acid rain chemistry. At ground level, it acts as a respiratory irritant and is part of photochemical smog.
*   **Sulfur dioxide (SO2)**: Reacts with water and oxidants to form sulfuric acid (H2SO4), a major constituent of acid rain.

Acid rain can lead to soil acidification, freshwater ecosystem disruption, damage to monuments, and adverse health effects on plants and animals.

IASCODEX · Answer

Option A: 1, 2, and 3

IASCODEX · Answer

Option C: 4 only

IASCODEX · Answer

Option D: 1, 3, and 4

Consider the following: Carbon monoxide Nitrogen oxide Ozone Sulphur dioxide Excess of which of the above in the environment is/are cause(s) of acid rain?

Consider the following:

Carbon monoxide

Nitrogen oxide

Ozone

Sulphur dioxide
Excess of which of the above in the environment is/are cause(s) of acid rain?