Assertion : Normal rain water has a pH of about 5.6.
Reason : The pH is due to dissolution of `CO_2` to form carbonic acid.

Options

A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C. Assertion is correct statement but reason is wrong statement
D. Assertion is wrong statement but reason is correct statement.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

**Assertion:** Normal rainwater has a pH of about 5.6.
**Reason:** The pH is due to the dissolution of CO2 to form carbonic acid.

### Step-by-Step Solution:

1. **Understanding Rainwater pH:**
- Normal rainwater has a pH of approximately 5.6. This is slightly acidic compared to pure water, which has a neutral pH of 7.

2. **Role of Carbon Dioxide (CO2):**
- The acidity of rainwater is primarily due to the presence of dissolved carbon dioxide (CO2) from the atmosphere.

3. **Formation of Carbonic Acid:**
- When CO2 dissolves in rainwater, it reacts with water (H2O) to form carbonic acid (H2CO3):
\[ H2O (l) + CO2 (g) \rightarrow H2CO3 (aq) \]

4. **Dissociation of Carbonic Acid:**
- Carbonic acid is a weak acid that partially dissociates in water to release hydrogen ions (H+) and bicarbonate ions (HCO3-):
\[ H2CO3 (aq) \rightleftharpoons H^+ (aq) + HCO3^- (aq) \]

5. **Effect on pH:**
- The release of hydrogen ions (H+) from the dissociation of carbonic acid is what lowers the pH of rainwater, making it slightly acidic.

6. **Conclusion:**
- Both the assertion and the reason are correct. The assertion states that normal rainwater has a pH of about 5.6, and the reason explains that this is due to the dissolution of CO2 forming carbonic acid, which contributes to the acidity.

### Final Answer:
- Both the assertion and the reason are correct, and the reason is the correct explanation for the assertion.