An exothermic reaction X to Y has an activation energy of 30 text kJ mol ^ -1 and energy change Delta E = -20 text kJ mol ^ -1 . What is the activation energy (in kJ) for the reverse reaction Y to X?

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EEJ MAIN Chemistry QUESTION #5538

Question 1

An exothermic reaction $X \to Y$ has an activation energy of $30\ \text{kJ mol}^{-1}$ and energy change $\Delta E = -20\ \text{kJ mol}^{-1}$. What is the activation energy (in kJ) for the reverse reaction $Y \to X$?

50✔️
10
20
30

Correct Answer Explanation

For an exothermic reaction: $E_{a(\text{forward})} = 30\ \text{kJ mol}^{-1}$, $\Delta E = -20\ \text{kJ mol}^{-1}$. Using energy profile: $E_{a(\text{reverse})} = E_{a(\text{forward})} - \Delta E = 30 - (-20) = 30 + 20 = 50\ \text{kJ mol}^{-1}$. The reverse (endothermic) reaction has a higher activation energy.

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