9.In rate expression, the concentration of reactants is negative. It shows

Explanation

The correct answer is:(c) Concentration of reactant decreasesHere's why the other options are incorrect:(a) Concentration of reactant does not change: This contradicts the very idea of a rate expression, which describes the change in concentration of reactants and products over time. In a reaction, reactants are consumed, so their concentration will always decrease.(b) Concentration of product increases: While the concentration of products increases as the reaction progresses, this isn't directly indicated by the sign of the reactant concentration term in the rate expression. The sign only refers to the change in reactant concentration.(d) Concentration of reactant increases: This is physically impossible in a typical chemical reaction. Reactants are consumed as the reaction proceeds, so their concentration cannot increase.Therefore, the negative sign in the concentration term of a rate expression indicates that the concentration of the reactant is decreasing with time. This negative value is then multiplied by a rate constant to determine the contribution of that reactant to the overall rate of the reaction.