Chemistry Reaction Kinetics MDCAT 2011
PMDC Verified Question 78 of 80
It is experimentally found that catalyst is used to:
A
Increase the activation energy
B
Lower the activation energy
C
Decrease the temperature of other reactants
D
Lower the pH
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Lower the activation energy
Concept:

A catalyst speeds up a chemical reaction without being consumed by providing an alternative reaction pathway.

Formula:

$$ E_{a(\text{catalyzed})} < E_{a(\text{uncatalyzed})} $$

Solution:

  • The primary function of a positive catalyst is to provide an alternative mechanism or pathway for the reaction.
  • This new pathway has a lower activation energy (\( E_a \)).
  • Because the barrier is lower, more molecules can react at a given temperature, accelerating the reaction.


Why other options are incorrect:

Increasing activation energy would slow the reaction (negative catalyst). Catalysts do not inherently alter the pH or change the bulk temperature of the reactants.

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