Changing the concentration of reactants and products in a reversible chemical reaction at equilibrium affects the reaction rate according to Le Chatelier's principle. This principle states that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust itself to counteract the change and restore a new equilibrium.When the concentration of reactants is increased, the reaction will shift towards the products to restore equilibrium. This means that the forward reaction rate will increase, and the reverse reaction rate will decrease. As a result, more products will be formed, and the equilibrium will be re-established.On the other hand, if the concentration of products is increased, the reaction will shift towards the reactants to restore equilibrium. In this case, the forward reaction rate will decrease, and the reverse reaction rate will increase. Consequently, more reactants will be formed, and the equilibrium will be re-established.In summary, changing the concentration of reactants and products in a reversible chemical reaction at equilibrium affects the reaction rate by causing the system to shift in the direction that counteracts the change, ultimately restoring a new equilibrium state.