The degree of hydrolysis of a salt of weak acid and weak base in it's 0.1 M solution is found to be 50%. If the molarity of the solution is 0.2 M, the percentage hydrolysis of the salt should be

Options

A. 1
B. 0.5
C. 0.25
D. None of these

Answer

To solve the problem, we need to determine the percentage hydrolysis of a salt of a weak acid and a weak base when the molarity of the solution is changed from 0.1 M to 0.2 M. Given that the degree of hydrolysis at 0.1 M is 50%, we can use the concept that the degree of hydrolysis is independent of concentration for weak acids and weak bases.

### Step-by-Step Solution:

1. **Understanding Hydrolysis**: Hydrolysis of a salt formed from a weak acid and a weak base leads to the formation of the respective weak acid and weak base in solution. The degree of hydrolysis (α) is defined as the fraction of the salt that undergoes hydrolysis.

2. **Given Information**:
- Initial molarity (C1) = 0.1 M
- Degree of hydrolysis at 0.1 M (α1) = 50% = 0.50

3. **Relationship of Hydrolysis Degree with Concentration**:
- For a salt of a weak acid and weak base, the degree of hydrolysis is independent of the concentration. Therefore, if the molarity of the solution is doubled, the degree of hydrolysis remains the same.

4. **Calculating for 0.2 M Solution**:
- New molarity (C2) = 0.2 M
- Since the degree of hydrolysis is independent of concentration, α2 (degree of hydrolysis at 0.2 M) will still be 50%.

5. **Percentage Hydrolysis**:
- Percentage hydrolysis at 0.2 M = α2 × 100% = 0.50 × 100% = 50%.

### Conclusion:
The percentage hydrolysis of the salt in a 0.2 M solution is **50%**.

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