Acid rain is due to

Options

A. formation of oxides of sulphur
B. formation of oxides of nitrogen
C. HCl
D. `HClO_(4)`

Answer

### Step-by-Step Solution:

1. **Understanding Acid Rain**: Acid rain refers to any form of precipitation (rain, snow, fog) that has a lower pH than normal, making it acidic. This phenomenon is primarily caused by the presence of certain acids in the atmosphere.

2. **Identifying the Sources of Acids**: The main contributors to acid rain are the oxides of sulfur and nitrogen. These oxides are released into the atmosphere through various human activities, particularly from industrial processes and automobile emissions.

3. **Formation of Sulfuric Acid**:
- Sulfur dioxide (SO₂) is released into the atmosphere.
- SO₂ reacts with oxygen (O₂) and water vapor (H₂O) to form sulfuric acid (H₂SO₄).
- The reaction can be summarized as:
\[ SO₂ + O₂ + H₂O \rightarrow H₂SO₄ \]

4. **Formation of Nitric Acid**:
- Nitrogen oxides (NO and NO₂) are also released into the atmosphere.
- NO₂ can react with O₂ to form nitric acid (HNO₃) through a series of reactions:
- NO₂ + O₂ → NO₃
- NO₃ + H₂O → HNO₃
- The overall reaction can be simplified to:
\[ NO₂ + H₂O \rightarrow HNO₃ \]

5. **Other Contributing Acids**: Carbon dioxide (CO₂) can also dissolve in rainwater to form carbonic acid (H₂CO₃), although it is a weaker acid compared to sulfuric and nitric acids:
\[ CO₂ + H₂O \rightarrow H₂CO₃ \]

6. **Conclusion**: The primary causes of acid rain are the formation of sulfuric acid from sulfur oxides and nitric acid from nitrogen oxides. These reactions lead to the acidification of precipitation.

### Final Answer:
Acid rain is due to the formation of oxides of sulfur (SO₂) and nitrogen (NO₂), which react in the atmosphere to produce strong acids like sulfuric acid (H₂SO₄) and nitric acid (HNO₃).

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