Question

A catalyst is a substance which:
A.Increases 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

A catalyst can be defined as a chemical or biological entity that enhances the rate of a chemical or a biological reaction. It decreases the activation energy and increases the rate of reaction.

Complete step by step answer:
- Every reactant converts to the products after crossing a certain energy barrier that is known as the “activation energy”. This is also known as the minimum amount of energy required to break the bonds of the reactant molecules for new products to form. The work of a catalyst is to lower this energy barrier or to reduce the amount of energy required for breaking the chemical bonds by providing an alternative pathway for the reaction to take place. But the catalyst itself does not undergo any change. The concentration of the catalyst before and after the reaction is constant.
- The first statement, “Increases the equilibrium concentration of the product” increases the rate of the reaction is false. The catalyst does not have any influence over the equilibrium constant also.
- The catalyst certainly shortens the time required to reach the equilibrium by providing an alternative route.The catalyst does not supply any energy to the reaction.

Hence, the correct option is C.

Note:
The catalyst does not have any influence over the equilibrium constant of a reaction because the catalyst only speeds up a forward or backward process and the dynamic equilibrium is established when the speed of the forward and the backward reactions are equal. As the catalyst speeds up both so the rate of the forward reaction as well as the backward reaction so the equilibrium is not changed.