The pH of a buffer solution containing 25 ml of 1 M `CH_(3)COONa " and 1 M " CH_(3)COOH` will be appreciably affected by

Options

A. `1 M CH_(3)COOH`
B. `5 M HCl`
C. `5M CH_(3)COOH`
D. `1M NH_(4)OH`

Answer

To determine how the pH of a buffer solution containing 25 ml of 1 M sodium acetate (CH₃COONa) and 1 M acetic acid (CH₃COOH) will be affected, we need to analyze the impact of adding different substances to the buffer system.

### Step-by-Step Solution:

1. **Understanding the Buffer System**:
- The buffer solution consists of a weak acid (CH₃COOH) and its conjugate base (CH₃COO⁻ from CH₃COONa).
- The pH of a buffer solution is relatively stable when small amounts of strong acids or bases are added.

2. **Identifying the Components**:
- CH₃COOH (acetic acid) is a weak acid that partially dissociates in solution.
- CH₃COONa (sodium acetate) dissociates completely in solution to give CH₃COO⁻ ions, which can react with added H⁺ ions.

3. **Analyzing the Effect of Adding 1 M Acetic Acid**:
- Adding 1 M acetic acid will increase the concentration of the weak acid but will not significantly change the pH because it is still a weak acid and does not dissociate completely.
- The buffer can accommodate this addition without a substantial change in pH.

4. **Analyzing the Effect of Adding 5 M HCl**:
- HCl is a strong acid and will completely dissociate, providing a high concentration of H⁺ ions (5 M).
- The excess H⁺ ions will react with the acetate ions (CH₃COO⁻) to form more acetic acid (CH₃COOH).
- This reaction will significantly lower the pH since the concentration of H⁺ ions is much higher than that of the buffer components.

5. **Analyzing the Effect of Adding 5 M Acetic Acid**:
- Similar to the 1 M acetic acid, adding 5 M acetic acid will increase the concentration of the weak acid.
- However, since it is still a weak acid, the change in pH will not be as significant as that caused by adding HCl.

6. **Analyzing the Effect of Adding 1 M Sodium Hydroxide (NaOH)**:
- NaOH is a strong base and will dissociate completely to provide OH⁻ ions.
- The OH⁻ ions will react with the weak acid (CH₃COOH) to form acetate ions (CH₃COO⁻) and water.
- This reaction will shift the equilibrium and can lead to a change in pH, but the buffer can moderate this change to some extent.

### Conclusion:
The pH of the buffer solution will be appreciably affected by adding **5 M HCl**, as it introduces a significant amount of H⁺ ions that can overwhelm the buffering capacity of the solution.