Q. Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R).
Assertion (A): CO₂, SO₂ and NO₂ gases get dissolved in rainwater and produce acid rain.
Reason (R): Atmospheric air is polluted due to high concentration of gases like carbon dioxide, sulphur dioxide and oxides of nitrogen.
Select the correct answer from the codes given below:
a) Both (A) and (R) are true and (R) is the correct explanation of (A).
b) (A) is false, but (R) is true.
c) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
d) (A) is true, but (R) is false.
Question from UPPSC Prelims 2024
Correct Answer: b) (A) is false, but (R) is true.
Explanation:
1. Primary Contributors to Acid Rain:
– Sulfur Dioxide (SO₂):
– Sources: Combustion of fossil fuels (like coal and oil), volcanic eruptions, and certain industrial processes.
– Chemical Reaction: SO₂ reacts with water vapor in the atmosphere to form sulfuric acid (H₂SO₄).
– Nitrogen Oxides (NOₓ), Mainly Nitrogen Dioxide (NO₂):
– Sources: Vehicle emissions, power plants, and industrial activities.
– Chemical Reaction: NO₂ reacts with water to produce nitric acid (HNO₃).
2. Carbon Dioxide (CO₂) and Its Role:
– Sources: Respiration, combustion of carbon-based fuels, deforestation, and various industrial activities.
– Chemical Reaction: CO₂ dissolves in water to form carbonic acid (H₂CO₃).
– Impact: While carbonic acid does contribute to the acidity of rainwater, it is a weak acid and has a negligible effect on the overall acidity compared to sulfuric and nitric acids. Consequently, CO₂ is not considered a primary cause of acid rain.
Analyzing the Given Statements
1. Assertion (A): “CO₂, SO₂, and NO₂ gases get dissolved in rainwater and produce acid rain.”
– Accuracy: Incorrect. While SO₂ and NO₂ are significant contributors to acid rain, CO₂ plays a minor role and is not a primary cause.
2. Reason (R): “Atmospheric air is polluted due to high concentration of gases like carbon dioxide, sulphur dioxide and oxides of nitrogen.”
– Accuracy: Correct. The statement accurately identifies CO₂, SO₂, and NOₓ (including NO₂) as major pollutants that contribute to various environmental issues, including pollution and acid rain.
