Question

A catalyst is a substance which
(A) Increase the equilibrium concentration of the product
(B) Changes the equilibrium constant of the reactant
(C) Shortens the time to reach equilibrium
(D) Supplies energy to the reaction

Answer 1

In this question we have been asked about the property of a catalyst in a chemical reaction so for that it will be referring to some example of catalyst and its function to find out which of the above options is correct.

Complete step by step answer:
As we know a catalyst is a substance that can be added to a reaction to increase the reaction rate without getting consumed in the process.
So, let’s take an example
$S{O_2} + {O_2} \mathop \to \limits^{Pt} S{O_3}$
- So, in the above reaction platinum is the catalyst and its function is to increase the rate of reaction without disturbing the equilibrium.
Catalyst are of two types, positive and negative catalyst:
- positive catalyst: when a catalyst increases the rate of chemical reaction.
- negative catalyst: when a catalyst decreases the rate of chemical reaction.
Therefore, we can say that a catalyst is a substance which shortens the time to reach equilibrium.

Note: In this question we should be a little bit cautious because of the option as it is mentioned that catalysts change the equilibrium condition and that’s definitely not the case although it shortens the time to reach equilibrium, so don’t get confused due to it. It will help in increasing the pace to reach equilibrium faster, when a positive catalyst is used.