The pH of normal rain water is

Options

A. 6.5
B. 7.5
C. 5.6
D. 3.5

Explanation

To determine the pH of normal rainwater, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Rainwater Composition**:
- Rainwater is primarily composed of water (H2O). However, it can also contain dissolved gases from the atmosphere.

2. **pH of Pure Water**:
- The pH of pure water at 25°C is 7.0. This is considered neutral.

3. **Effect of Atmospheric Gases**:
- In the atmosphere, gases such as carbon dioxide (CO2), sulfur dioxide (SO2), and nitrogen oxides (NOx) can dissolve in rainwater.
- The presence of these gases can affect the pH of rainwater.

4. **Formation of Acids**:
- When CO2 dissolves in water, it forms carbonic acid (H2CO3), which can lower the pH.
- Similarly, SO2 can form sulfurous acid (H2SO3) and SO3 can form sulfuric acid (H2SO4) when dissolved in water.

5. **Normal Rainwater pH**:
- In the absence of significant pollution, the pH of normal rainwater is typically around 5.6 due to the presence of dissolved CO2, which forms a weak acid.
- However, in clear weather with no impurities, the pH can be around 6.5.

6. **Conclusion**:
- Therefore, the pH of normal rainwater, considering the presence of natural atmospheric gases, is approximately 5.6 to 6.5, with the average value often cited as about 5.6.

### Final Answer:
The pH of normal rainwater is approximately 5.6 to 6.5.

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