Question

Which one of the following changes when a catalyst is used in a reaction?
A. Heat of the reaction
B. Product of reaction
C. Equilibrium constant
D. Activation energy

Answer 1

Hint: A catalyst when used in a reaction makes the reaction faster. This is because the catalyst facilitates an alternate pathway for the reaction to occur. Some names of catalysts are nickel, palladium, etc.

Complete Step by Step Answer:
Let's understand what happens with the catalyst addition to a system. The role of the catalyst is to speed up both the forward and the backward reactions. Thus, it helps to achieve the equilibrium state early. But the concentration at equilibrium is not changed, that is, the equilibrium constant is not changed.

Let's discuss the options one by one.
The heat of the reaction is the same with the addition of catalysts. Therefore, option A is incorrect.
The product of the reaction does not change with the addition of catalysts. Therefore, option B is wrong.
There is no change of equilibrium constant on the addition of catalysts. Therefore, option C is wrong.
Activation energy defines the minimum quantity of energy needed by the molecules of reactants to give a chemical reaction. The catalyst reduces the activation energy, facilitates an alternate pathway for the reaction, and makes the reaction faster.
Therefore, option D is right.

Note: Catalysts are classified as positive and negative catalysts. Positive catalysts speed up reactions, namely, manganese dioxide, vanadium dioxide, etc. The negative catalysts lower the speed of a reaction, such as platinum.