Changing the concentration of a reactant affects the rate of a chemical reaction because it influences the frequency of collisions between reactant particles. According to the collision theory, the rate of a reaction depends on the number of effective collisions between reactant particles per unit time. When the concentration of a reactant is increased, there are more particles in the same volume, leading to a higher probability of collisions and thus a faster reaction rate.This relationship can be quantified using experimental data by studying the reaction rate at different concentrations of the reactant. The rate law is an equation that expresses the reaction rate as a function of the concentrations of the reactants. The general form of the rate law for a reaction involving reactants A and B is: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.To determine the reaction orders m and n and the rate constant k , you can perform a series of experiments at different initial concentrations of the reactants and measure the initial reaction rates. By plotting the data and analyzing the relationship between the reaction rate and the concentrations, you can determine the reaction orders and the rate constant.For example, if you find that doubling the concentration of reactant A doubles the reaction rate, the reaction order with respect to A m would be 1. If tripling the concentration of reactant B increases the reaction rate by a factor of 9, the reaction order with respect to B n would be 2. Once you have the reaction orders, you can use the rate law equation to calculate the rate constant k for the reaction.In summary, changing the concentration of a reactant affects the rate of a chemical reaction, and this relationship can be quantified using experimental data by determining the reaction orders and rate constant through the rate law equation.