Assertion: Law of mass action states that rate of chemical reaction is proportional to the product of the active masses of the reacting substances, raised to the power, equal to the respective number of their molecules taking part in a reaction as represented by the balanced chemical equation.

Reason: Law of mass action is applicable to both elementary as well as complex reactions.

Assertion is correct statement but reason is wrong statement.

Law of mass action states that rate of chemical reaction is proportional to the product of the active masses of the reacting substances, raised to the power, equal to the respective number of their molecules taking part in a reaction as represented by the balanced chemical equation. But it is applicable to only elementary reactions.