In which of the following case, equlibrium constant decreases with increase of temperture

Options

A. When the reaction is exothermic
B. When the reaction is endothermic
C. When the reaction is in the gaseous phase
D. When the reaction takes place in the solution

Explanation

To determine in which case the equilibrium constant decreases with an increase in temperature, we need to analyze the relationship between temperature and equilibrium constants for different types of reactions.

### Step-by-Step Solution:

1. **Understand the Concept of Equilibrium Constant (K)**:
- The equilibrium constant (K) is a value that expresses the ratio of the concentration of products to the concentration of reactants at equilibrium for a given reaction at a specific temperature.

2. **Identify the Types of Reactions**:
- Reactions can be classified as either exothermic or endothermic.
- **Exothermic Reaction**: A reaction that releases heat (ΔH < 0).
- **Endothermic Reaction**: A reaction that absorbs heat (ΔH > 0).

3. **Effect of Temperature on Exothermic Reactions**:
- For exothermic reactions, as the temperature increases, the equilibrium constant (K) decreases. This is because adding heat shifts the equilibrium position to favor the reactants, thus reducing the value of K.
- Therefore, there is an **inverse relationship** between temperature and K for exothermic reactions.

4. **Effect of Temperature on Endothermic Reactions**:
- For endothermic reactions, as the temperature increases, the equilibrium constant (K) increases. This is because adding heat shifts the equilibrium position to favor the products, thus increasing the value of K.
- Hence, there is a **direct relationship** between temperature and K for endothermic reactions.

5. **Conclusion**:
- The equilibrium constant decreases with an increase in temperature for exothermic reactions. Therefore, the answer to the question is that the equilibrium constant decreases with an increase in temperature when the reaction is exothermic.

### Final Answer:
The equilibrium constant decreases with an increase in temperature for **exothermic reactions**.

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