Chemistry Reaction Kinetics NUMS 2019
PMDC Verified Question 51 of 80
If energy of activated complex is close to energy of reactants, it means that the reaction is:
A
Slow
B
Moderate
C
Fast
D
Very slow
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Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Fast
Concept:

The rate of a chemical reaction is inversely dependent on its activation energy. A smaller energy gap means a faster reaction.

Formula:

$$ E_{a} = E_{\text{activated complex}} - E_{\text{reactants}} $$

Solution:

  • If the energy of the activated complex is very close to the energy of the reactants, the activation energy (\( E_a \)) is very low.
  • A low activation energy means a larger fraction of reactant molecules will possess enough kinetic energy to cross the barrier at any given temperature.
  • Therefore, the reaction proceeds extremely fast.


Why other options are incorrect:

Slow or moderate reactions imply a significantly higher activation energy barrier that fewer molecules can successfully overcome.

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