Activation Energy

Step 1: Formula
For any reaction, the relationship between forward activation energy ( ), backward activation energy ( ), and enthalpy change ( ) is: .
Step 2: Values
.
Since the reaction is exothermic, the heat released is 200 kJ, so .
Step 3: Calculation

.
Final Answer: (D)

Step 1: Understanding the Concept:
For an exothermic reaction, .

Step 2: Detailed Explanation:
Given: kcal (endothermic as written, but reaction is exothermic? Check sign: N + 3H → 2NH is exothermic, so kcal).
Assuming kcal (exothermic),
kcal.

Step 3: Final Answer:
+72 kcal