Chemistry Macromolecules / Biochemistry MDCAT 2018
PMDC Verified Question 42 of 47
Role of a catalyst in a chemical reaction is to
A
Decrease rate of a reaction
B
Increase rate of a reaction
C
Decrease yield of a reaction
D
Increase yield of product
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Increase rate of a reaction
Concept:

Catalysts (including biological enzymes) affect the kinetics of a chemical reaction without altering its thermodynamics.

Formula:

$$ k = A e^{-\frac{E_a}{RT}} $$

Solution:

  • A catalyst provides an alternative reaction pathway with a lower activation energy (\( E_a \)).
  • By lowering \( E_a \), a larger proportion of reactant molecules possess sufficient kinetic energy to react, thereby increasing the rate of the reaction.
  • It does not change the equilibrium constant or the final yield of the products.


Why other options are incorrect:

Catalysts do not decrease the reaction rate (that is the role of an inhibitor). They also cannot change the thermodynamic yield of the reaction; they only help the reaction reach equilibrium faster.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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