Changing the concentration of reactants in a reaction mechanism can significantly impact the rate of the overall reaction. This is explained by the collision theory and the rate law.According to the collision theory, a chemical reaction occurs when reactant molecules collide with sufficient energy and proper orientation. When the concentration of reactants is increased, the number of reactant molecules in the reaction mixture also increases. This leads to a higher probability of successful collisions between reactant molecules, resulting in an increased rate of reaction.The rate law is a mathematical expression that relates the rate of a reaction to the concentrations of the reactants. It is usually expressed as:Rate = k[A]^m[B]^nwhere Rate is the reaction rate, k is the rate constant, [A] and [B] are the concentrations of reactants A and B, and m and n are the reaction orders with respect to A and B, respectively.The reaction orders m and n indicate how the rate of the reaction is affected by the concentration of each reactant. If the reaction order is positive, an increase in the concentration of the reactant will lead to an increase in the reaction rate. If the reaction order is negative, an increase in the concentration of the reactant will lead to a decrease in the reaction rate. If the reaction order is zero, the reaction rate is not affected by the concentration of the reactant.In summary, changing the concentration of reactants in a reaction mechanism can impact the rate of the overall reaction by altering the frequency of successful collisions between reactant molecules and by affecting the reaction rate according to the rate law. The specific impact on the reaction rate depends on the reaction orders of the reactants involved.