Which of the following will not affect the value of equilibrium constant of a reaction?

Options

A. Change in the concentration of the reactants
B. Change in temperature
C. Change in pressure
D. Addition of catalyst

Answer

To determine which factor does not affect the equilibrium constant of a reaction, we need to understand the factors that influence it.

### Step-by-Step Solution:

1. **Understanding Equilibrium Constant (K)**:
The equilibrium constant (K) for a reaction at equilibrium is defined as the ratio of the concentrations of the products to the concentrations of the reactants, each raised to the power of their coefficients in the balanced chemical equation.

2. **Factors Affecting Equilibrium Constant**:
- **Temperature**: Changing the temperature of a reaction will change the equilibrium constant. For exothermic reactions, increasing the temperature decreases K, while for endothermic reactions, increasing the temperature increases K.
- **Pressure**: For reactions involving gases, changing the pressure can shift the position of equilibrium, but it does not change the value of K unless the temperature is also changed.
- **Concentration**: Changing the concentration of either reactants or products will shift the position of equilibrium but will not change the value of K.

3. **Role of Catalysts**:
- A catalyst speeds up the rate at which equilibrium is reached but does not change the position of equilibrium or the equilibrium constant. It does not affect the concentrations of reactants and products at equilibrium.

4. **Conclusion**:
From the above analysis, we can conclude that the factor that does not affect the value of the equilibrium constant is the addition of a catalyst.

### Final Answer:
The addition of a catalyst will not affect the value of the equilibrium constant of a reaction.

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