A : Rate constant increases with temperature.
R : Rate of exothermic reaction increases with temperature.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion , then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements , then mark (4)

Answer

To analyze the given statements, we need to evaluate both the Assertion (A) and the Reason (R) in the context of chemical kinetics.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that the rate constant (k) increases with temperature.
- This can be explained using the Arrhenius equation:
\[ k = A e^{-\frac{E_a}{RT}} \]
- Here, \(k\) is the rate constant, \(A\) is the pre-exponential factor, \(E_a\) is the activation energy, \(R\) is the universal gas constant, and \(T\) is the temperature in Kelvin.

2. **Effect of Temperature on Rate Constant**:
- As temperature (T) increases, the term \(-\frac{E_a}{RT}\) becomes less negative, leading to an increase in the value of \(k\).
- Therefore, the assertion that the rate constant increases with temperature is **true**.

3. **Understanding the Reason (R)**:
- The reason states that the rate of exothermic reactions increases with temperature.
- While it is true that the rate of many reactions increases with temperature, for exothermic reactions, the increase in rate is not as straightforward as it is for endothermic reactions.

4. **Analyzing the Relationship**:
- The rate of a reaction is influenced by the rate constant (k) and the concentration of reactants.
- For exothermic reactions, while the rate constant increases with temperature, the overall effect on the reaction rate can be complex due to the nature of the reaction and the equilibrium position.

5. **Conclusion**:
- Both the assertion (A) and the reason (R) are true. However, the reason does not directly explain the assertion. The rate of exothermic reactions may increase with temperature, but it is not a direct consequence of the assertion regarding the rate constant.

### Final Evaluation:
- **Assertion (A)**: True
- **Reason (R)**: True
- **Conclusion**: The reason does not explain the assertion.