The role of catalyst is to change:

The correct answer is Option (3) → Activation energy of the reaction

A catalyst takes part in the reaction through temporary bonds with the reactants and is given back unchanged at the end. It provides an alternative pathway of lower activation energy, so a larger fraction of molecules can cross the energy barrier and the reaction becomes faster.

The catalyst lowers the barrier for the forward and the backward reaction equally. It does not change the energies of the reactants and products, so the enthalpy, the Gibbs energy and the equilibrium constant of the reaction stay the same; equilibrium is only reached sooner.

Why the other options are incorrect

• Option (1) Gibbs energy of reaction — Incorrect. \( \Delta G \) depends only on the initial and final states, which the catalyst does not change; a catalyst cannot make a non-spontaneous reaction spontaneous.

• Option (2) Enthalpy of reaction — Incorrect. The reactants and products have the same energies with or without the catalyst, so \( \Delta H \) is unchanged.

• Option (4) Equilibrium constant — Incorrect. Both forward and backward rates rise by the same factor, so their ratio, the equilibrium constant, is unchanged.

NCERT (2026-27 edition):
Effect of Catalyst – …

Note: The same/similar question has been asked in different years by NTA as per the details given below: