Question

The use of catalyst in chemical reaction _________ activation energy of a reaction.
[A] Increases
[B] Decreases
[C] Maintains
[D] None of these.

Answer 1

Hint: A catalyst increases the rate of reaction by affecting the activation energy of the reaction. We can form a product faster if we can make the reactants choose a lower energy pathway.

Complete answer:
We know that a catalyst is a compound which helps a chemical reaction to move in the forward direction without itself taking part in the reaction. Basically we can say that a catalyst enhances the rate of a chemical reaction. A catalyst will not hinder the formation of a product or case any change in the composition or mass of the product. To answer this question, we have to understand how a catalyst affects the activation energy of a chemical reaction.

As we know, activation energy is the minimum energy which is required by the reactant in order to turn into a product. Compounds with higher activation energy will need a higher energy to be converted to product. In simple words, we can say that lower activation energy makes it form the product.
We know that the function of a catalyst is to increase the speed of reaction and it does that by bringing down the activation energy so that a larger amount of particles have enough energy to react. A catalyst can bring down the activation energy by orienting the reactant particles in such a way that they collide successfully with each other or by reacting with the reactants and form an intermediate which will require a lower energy compared to the original starting reactant to form the product.
In the Haber’s process of making ammonia we add iron oxide which acts as a catalyst and also increases the yield of ammonia.
As we can understand from the above discussion, the use of catalyst in chemical reaction decreases activation energy of a reaction.
So, the correct answer is “Option B”.

Note: We discussed the catalysts which increase the rate of reaction in the above discussion but there also exists a negative catalyst which decreases the rate of a chemical reaction. Negative catalysts increase the activation energy and combine with the reactant particles so that they cannot collide to form the product. Ethanol acts as a negative catalyst in the oxidation of chloroform.