Chemistry Reaction Kinetics MDCAT 2019
PMDC Verified Question 60 of 80
What is the measure of activation energy is an endothermic reaction?
A
The energy of activation of backward reaction is less than that of forward reaction
B
The energy of activation of forward-backward reaction is same
C
The energy of activation of backward reaction is more than that of forward reaction
D
The energy of activation of forward reaction is less than that of backward reaction
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: The energy of activation of backward reaction is less than that of forward reaction
Concept:

In an endothermic profile, heat is absorbed, leaving products at a higher potential energy state than the reactants.

Formula:

$$ \Delta H = E_{a(\text{forward})} - E_{a(\text{backward})} > 0 $$

Solution:

  • Since \( \Delta H \) is positive, \( E_{a(\text{forward})} \) must be mathematically greater than \( E_{a(\text{backward})} \).
  • This means the backward reaction has a smaller energy hill to climb to reach the transition state compared to the forward reaction.


Why other options are incorrect:

If backward is more, the reaction is exothermic. If they are equal, there is no net energy change.

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