Which of the following is true for catalysts?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → It provides an alternate pathway or reaction mechanism.
A catalyst increases the rate of a reaction without being used up. It does this by providing an alternate pathway (reaction mechanism) with a lower activation energy. More molecules then have enough energy to react, so the reaction becomes faster.
A catalyst takes part in the steps of the reaction but is regenerated at the end. It lowers the energy barrier equally for the forward and the backward reactions and does not change the energies of the reactants or the products.
Why the other options are incorrect
Option (1) It alters the equilibrium constant. — Incorrect. A catalyst speeds up the forward and backward reactions equally, so equilibrium is reached sooner, but the equilibrium constant is not changed.
Option (2) It catalyzes non-spontaneous reaction. — Incorrect. A catalyst can speed up only a reaction that is already spontaneous (ΔG negative); it cannot make a non-spontaneous reaction take place.
Option (4) It alters the Gibbs free energy of a reaction. — Incorrect. ΔG depends only on the initial and final states, which a catalyst does not change.
NCERT (2026-27 edition):
Effect of Catalyst – “… It is believed that the catalyst provides an alternate pathway or reaction mechanism by reducing the activation energy between reactants and products and hence lowering the potential energy barrier as shown in Fig. 3.11. It is clear from Arrhenius equation (3.18) that lower the value of activation energy faster will be the rate of a reaction. A small amount of the catalyst can catalyse a large amount of reactants. A catalyst does not alter Gibbs energy, ΔG of a reaction. It catalyses the spontaneous reactions but does not catalyse non-spontaneous reactions. It is also found that a catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster, that is, it catalyses the forward as well as the backward reactions to the same extent so that the equilibrium state remains same but is reached earlier.”
