Chemistry Reaction Kinetics DUHS 2022
PMDC Verified Question 35 of 80
Rate of reaction increases by the addition of catalyst because:
A
Catalyst reacts with reactant
B
Catalyst reacts with product
C
Energy of activation decreases
D
Energy of activation increases
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Energy of activation decreases
Concept:

A catalyst provides a new reaction mechanism that requires less energy to reach the transition state.

Formula:

$$ k = A e^{-E_a / RT} $$

Solution:

  • By lowering the activation energy (\( E_a \)), a much larger percentage of colliding reactant molecules possess enough energy to successfully cross the barrier.
  • According to the Arrhenius equation, a smaller \( E_a \) in the negative exponent dramatically increases the rate constant \( k \).


Why other options are incorrect:

Increasing activation energy slows down a reaction. While catalysts do form temporary intermediate bonds with reactants (Option A), the fundamental thermodynamic reason the rate increases is specifically the decrease in the activation energy barrier.

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