Question

A catalyst is a substance which:
A. Increase the equilibrium concentration of the product.
B. changes the equilibrium constant of the reaction.
C. shortens the time to reach equilibrium.
D. supplies energy to the reaction.

Answer 1

Hint: To solve this question, we have to remember that catalyst is a substance which alters the rate of reaction without itself undergoing any permanent change.

Complete step by step answer:
The action of a catalyst can be explained by intermediate complex theory. A catalyst participates in a chemical reaction, according to this theory, by forming temporary bonds with the reactants, resulting in an intermediate complex. This has a transitory life and decomposes in order to generate the catalyst and products.
A small amount of catalyst can catalyse a large amount of reactants. It is also found that a catalyst does not modify a reaction's equilibrium constant, but rather helps to achieve equilibrium faster, which is to catalyse the forward as the backward reactions to the same degree such that the state of equilibrium stays the same but is previously reached.
Hence, we can say that a catalyst shortens the time to reach equilibrium.
So, the correct answer is “Option C”.

Note: It is believed that a catalyst provides an alternate pathway or reaction mechanism by reducing the activation energy between reactants and products and hence lowers the potential energy barrier.