Which action will slow down the rate of a reaction

A. Increasing the concentration of the reactants

B. Adding a catalyst to the reaction

C. Raising the temperature of the reactants

D. Decreasing surface area of a solid reactant

Answer is - Decreasing surface area of a solid reactant, rate of reaction can be slowed down.

Explanation: The quantity of a reactant species consumed or the quantity of product species formed in unit time in a chemical reaction is called rate of reaction. With passage of time, concentration of reactant decreases and concentration of product increases. Rate of reaction depends on various factors like - concentration of reactant, temperature, nature of reactant, catalyst and surface area of reactant.

By increasing the concentration of the reactants, rate of the reaction increases.

Presence of catalyst increases the rate of reaction.

With increase in temperature, kinetic energy of molecules increases which results to more number of effective collisions, so, rate of reaction increases.

With increase in the surface area of reactant, more number of molecules can react at a time and by decreasing the surface area of solid reactant rate of the reaction will diminish / decrease.