A : For exothermic reaction,
`DeltaH=E_a` (forward) `-E_a` (backward)
R : The value of activation energy for forward direction is less than activation energy for backward reaction.

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 regarding the Assertion (A) and Reason (R) statements about exothermic reactions and activation energies, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that for an exothermic reaction, the change in enthalpy (ΔH) is equal to the activation energy of the forward reaction (E_a forward) minus the activation energy of the backward reaction (E_a backward).
- Mathematically, this can be expressed as:
\[ ΔH = E_a \text{(forward)} - E_a \text{(backward)} \]

2. **Understanding the Reason (R)**:
- The reason states that the activation energy for the forward direction is less than the activation energy for the backward reaction.
- This can be expressed as:
\[ E_a \text{(forward)} < E_a \text{(backward)} \]

3. **Analyzing the Relationship**:
- In an exothermic reaction, the products have lower energy than the reactants. Therefore, the enthalpy change (ΔH) is negative.
- For ΔH to be negative in the equation \( ΔH = E_a \text{(forward)} - E_a \text{(backward)} \), it implies that:
\[ E_a \text{(forward)} < E_a \text{(backward)} \]
- This confirms that the forward activation energy must be less than the backward activation energy for the reaction to be exothermic.

4. **Conclusion**:
- Both the assertion and the reason are true.
- The reason correctly explains why the assertion is true because the relationship between the activation energies is necessary for the enthalpy change to be negative in an exothermic reaction.

### Final Answer:
Both Assertion (A) and Reason (R) are true, and the Reason (R) is the correct explanation for Assertion (A).

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