The effect of changing the concentration of reactants on the reaction rate can be explained using the collision theory. According to this theory, a reaction occurs when reactant particles collide with the proper orientation and sufficient energy. When the concentration of reactants increases, the number of particles in a given volume also increases, leading to a higher probability of effective collisions and, consequently, a faster reaction rate.However, the relationship between concentration and reaction rate can differ for reactions with different mechanisms. Reaction mechanisms are the step-by-step processes through which reactants are converted into products. These mechanisms can involve one or more elementary steps, each with its own rate law.For a simple one-step reaction, the reaction rate is directly proportional to the concentration of the reactants raised to their respective reaction orders. The overall reaction order is the sum of the individual reaction orders. For example, for a reaction with the rate law: rate = k[A]^m[B]^n, increasing the concentration of A or B will increase the reaction rate according to the exponents m and n.For reactions with multiple steps, the relationship between concentration and reaction rate can be more complex. In these cases, the rate-determining step the slowest step in the mechanism governs the overall reaction rate. The rate law for the overall reaction will depend on the rate law for the rate-determining step, which in turn depends on the concentrations of the species involved in that step.In summary, changing the concentration of reactants generally affects the reaction rate, but the specific relationship depends on the reaction mechanism and the rate laws for the elementary steps involved. For simple one-step reactions, the reaction rate is directly proportional to the concentration of reactants raised to their respective reaction orders, while for multi-step reactions, the rate-determining step governs the overall reaction rate and its dependence on reactant concentrations.