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 solve the question, we need to analyze both the assertion (A) and the reason (R) given in the statement.

### Step 1: Analyze the Assertion (A)
The assertion states that "Rate constant increases with temperature."

- According to the Arrhenius equation, the rate constant (k) is given by:
\[ k = A e^{-\frac{E_a}{RT}} \]
where:
- \( A \) is the pre-exponential factor,
- \( E_a \) is the activation energy,
- \( R \) is the universal gas constant,
- \( T \) is the temperature in Kelvin.

- As temperature (T) increases, the term \(-\frac{E_a}{RT}\) becomes less negative, which means that \( e^{-\frac{E_a}{RT}} \) increases. Therefore, the rate constant \( k \) increases with an increase in temperature.

**Conclusion for Assertion (A): True**

### Step 2: Analyze the Reason (R)
The reason states that "Rate of exothermic reaction increases with temperature."

- In an exothermic reaction, heat is released as a product. When the temperature of an exothermic reaction is increased, the reaction shifts towards the reactants according to Le Chatelier's principle. This means that the rate of the forward reaction (which produces heat) actually decreases because the system tries to counteract the increase in temperature by favoring the endothermic direction (the reverse reaction).

**Conclusion for Reason (R): False**

### Step 3: Final Conclusion
- Since the assertion is true and the reason is false, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- The correct option is **C**: Assertion is true, Reason is false.

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