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 which addition will appreciably affect the pH of a buffer solution containing 25 ml of 1 M sodium acetate (CH₃COONa) and 1 M acetic acid (CH₃COOH), we will analyze the effect of different substances on the buffer system.

### Step-by-Step Solution:

1. **Understanding the Buffer System**:
- The buffer solution consists of a weak acid (acetic acid, CH₃COOH) and its conjugate base (sodium acetate, CH₃COONa).
- Buffers resist changes in pH upon the addition of small amounts of acids or bases.

2. **Analyzing the Effect of Adding Acetic Acid (1 M)**:
- Adding more acetic acid (1 M) to the buffer will increase the concentration of CH₃COOH.
- However, since acetic acid is a weak acid and does not dissociate completely, the increase in H⁺ concentration will not be significant enough to appreciably change the pH.

3. **Analyzing the Effect of Adding Hydrochloric Acid (5 M)**:
- Adding 5 M HCl, a strong acid, will lead to complete dissociation, resulting in a high concentration of H⁺ ions.
- The presence of excess H⁺ ions will shift the equilibrium of the buffer system, leading to a significant decrease in pH. Thus, this will appreciably affect the pH.

4. **Analyzing the Effect of Adding Acetic Acid (5 M)**:
- Similar to the first case, adding 5 M acetic acid will increase the concentration of CH₃COOH.
- However, since acetic acid is a weak acid, it will not dissociate completely, and the increase in H⁺ concentration will still be less than that of a strong acid like HCl. Therefore, it will not appreciably affect the pH.

5. **Analyzing the Effect of Adding Ammonium Hydroxide (1 M)**:
- Ammonium hydroxide (NH₄OH) is a weak base and will produce OH⁻ ions upon dissociation.
- The addition of a weak base will not significantly change the pH of the buffer solution, as the buffer can neutralize the added base effectively.

### Conclusion:
Among the substances analyzed, the addition of **5 M HCl** will appreciably affect the pH of the buffer solution due to the high concentration of H⁺ ions it introduces.

### Final Answer:
**The pH of the buffer solution will be appreciably affected by the addition of 5 M HCl.**

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