Question:medium

Sulphur dioxide is one of the components of polluted air. SO2 is also a major contributor to acid rain. The correct and complete reaction to represent acid rain caused by SO2 is

Updated On: Mar 18, 2026
  • 2SO2 + O2 → 2SO3
  • SO2 + O3 → SO3 + O2
  • SO2 + H2O2 → H2SO4
  • 2SO2 + O2 + 2H2O → 2H2SO4
Show Solution

The Correct Option is D

Solution and Explanation

 The problem requires determining the complete chemical reaction illustrating how sulphur dioxide (SO2), a component of polluted air, contributes to acid rain.

Let's analyze each option to identify the correct and thorough reaction for acid rain caused by SO2:

  1. 2SO2 + O2 → 2SO3
    • This reaction shows sulphur dioxide being oxidized to form sulphur trioxide (SO3) in the presence of oxygen. However, it does not include the formation of sulfuric acid (H2SO4), which is essential to represent the contribution to acid rain.
  2. SO2 + O3 → SO3 + O2
    • This reaction shows SO2 reacting with ozone (O3) to form SO3. Similar to the first option, it does not directly result in the formation of H2SO4. Therefore, it is incomplete for representing acid rain.
  3. SO2 + H2O2 → H2SO4
    • This reaction suggests that SO2 reacts with hydrogen peroxide (H2O2) to produce sulfuric acid. Although it forms H2SO4, it’s not the conventional pathway involving atmospheric oxygen essential for acid rain processes.
  4. 2SO2 + O2 + 2H2O → 2H2SO4
    • This reaction is the comprehensive reaction showing how sulphur dioxide (SO2) reacts with oxygen (O2) and water (H2O) to form sulfuric acid. It correctly represents the atmospheric processes leading to acid rain, involving the oxidation of SO2 and its subsequent combination with water.

Conclusion: The correct answer is the reaction 2SO2 + O2 + 2H2O → 2H2SO4, as it accurately signifies the transformation of polluted air components into acid rain.

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