In equilibrium `CH_(3)COOH+H_(2)OhArrCH_(3)COO^(-)+H_(3)O^(+)`
The equilibrium constant may change when

Options

A. `CH_(3)COO^(-)` is added
B. `CH_(3)COOH` is added
C. Catalyst is added
D. Mixture is heated

Answer

To determine when the equilibrium constant for the reaction

\[ \text{CH}_3\text{COOH} + \text{H}_2\text{O} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}_3\text{O}^+ \]

may change, we need to analyze the effects of various factors on the equilibrium constant \( K_{eq} \).

### Step-by-Step Solution:

1. **Understanding the Equilibrium Constant**:
The equilibrium constant \( K_{eq} \) for the reaction can be expressed as:
\[ K_{eq} = \frac{[\text{CH}_3\text{COO}^-][\text{H}_3\text{O}^+]}{[\text{CH}_3\text{COOH}]} \]
Note that the concentration of water \([\text{H}_2\text{O}]\) is not included in the expression because it is a pure liquid.

2. **Effect of Concentration Changes**:
- **Adding CH₃COO⁻ (Product)**:
When you add more CH₃COO⁻, the concentration of the products increases. According to Le Chatelier's principle, the equilibrium will shift to the left to counteract this change, but the value of \( K_{eq} \) remains unchanged.
- **Adding CH₃COOH (Reactant)**:
Similarly, if you add more CH₃COOH, the concentration of reactants increases. The equilibrium will shift to the right, but again, \( K_{eq} \) remains unchanged.

3. **Effect of Catalysts**:
- **Adding a Catalyst**:
A catalyst speeds up the rate of both the forward and reverse reactions equally, thus it does not affect the position of equilibrium or the value of \( K_{eq} \). Therefore, the equilibrium constant remains unchanged.

4. **Effect of Temperature**:
- **Heating the Mixture**:
According to the Van't Hoff equation, the equilibrium constant is dependent on temperature. If the temperature of the system is changed, the equilibrium constant \( K_{eq} \) will also change. This is the only factor among the options that affects the equilibrium constant.

### Conclusion:
The equilibrium constant \( K_{eq} \) may change when the temperature of the system is altered. Therefore, the correct answer is:

**The equilibrium constant may change when the mixture is heated.**