Answer: Option (d) is the correct answer.
Explanation:
A catalyst is defined as a substance which helps in increasing the rate of a chemical reaction. This is because a catalyst lowers the activation energy and hence, more number of reactant molecules can take part in the chemical reaction.
This causes an increase in the rate of a chemical reaction.
According to law of mass action, when we decrease the concentration of reactants then there will also occur a decrease in concentration of the products. Hence, rate of reaction will decrease upon decrease in the concentration of reactants.
Also, removing heat energy from the reactants will lead to a decrease in the kinetic energy of molecules due to which they are unable to participate in the reaction. Therefore, rate of reaction will also decrease.
Thus, we can conclude that adding a catalyst to the reactants is usually associated with a faster reaction rate.
