What overall effect does adding a catalyst have on a chemical reaction? it increases pressure on the system. it increases reactant surface area. it lowers the activation energy that is needed. it lowers the concentration of reactants.

Option (c) is the correct answer.

Explanation:

A catalyst is a substance which increases the rate of a reaction without itself getting consumed in the chemical reaction.

Activation energy is the amount of energy required by the reacting species to undergo a chemical reaction.

A catalyst lowers the activation energy that is needed for the reaction.

Before the addition of a catalyst in a chemical reaction, the particles are moving by crossing a high energy path. The particles which have low energy were not able to cross this high energy path. Therefore, this path acts as a  barrier for particles with low energy. Hence, low energy particles were not able to participate in the reaction.

On addition of a catalyst, the activation energy decreases and hence the path of reaction changes. Therefore, the particles with low energy can now cross this new energy barrier and hence, they can also participate in the reaction.

Hence, the rate of reaction will also increase.