To a solution containing equimolar mixture of sodium acetate and acetic acid, some more amount of sodium acetate solution is adde. The pH of mixture solution.

Options

A. increases
B. decreases
C. remains same
D. none of these can be predicted from given information

Answer

To solve the problem regarding the pH of a solution containing an equimolar mixture of sodium acetate and acetic acid after adding more sodium acetate, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- We have an equimolar mixture of sodium acetate (CH₃COONa) and acetic acid (CH₃COOH).
- Sodium acetate is a salt derived from a weak acid (acetic acid) and a strong base (sodium hydroxide).

2. **Buffer Solution Concept**:
- The mixture of acetic acid and sodium acetate forms a buffer solution. A buffer solution resists changes in pH when small amounts of acid or base are added.
- The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation:
\[ \text{pH} = \text{pK}_a + \log\left(\frac{[\text{A}^-]}{[\text{HA}]}\right) \]
- Here, \([\text{A}^-]\) is the concentration of the acetate ion (from sodium acetate) and \([\text{HA}]\) is the concentration of acetic acid.

3. **Adding More Sodium Acetate**:
- When more sodium acetate is added to the solution, the concentration of the acetate ion \([\text{A}^-]\) increases.
- However, since we are adding it to a buffer solution, the pH will not change significantly because the buffer system can accommodate the change in concentration.

4. **Conclusion**:
- Since the pH of a buffer solution remains relatively constant despite changes in the concentrations of its components, the pH of the mixture will remain the same after adding more sodium acetate.

5. **Final Answer**:
- Therefore, the pH of the mixture solution remains unchanged after the addition of sodium acetate.