Changing the concentration of reactants or products in a chemical reaction at equilibrium affects the rate of the reaction 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 system will shift towards the products to counteract the change, thus increasing the rate of the forward reaction. Conversely, if the concentration of products is increased, the system will shift towards the reactants, increasing the rate of the reverse reaction.Similarly, if the concentration of reactants is decreased, the system will shift towards the reactants, increasing the rate of the reverse reaction. If the concentration of products is decreased, the system will shift towards the products, increasing the rate of the forward reaction.In summary, changing the concentration of reactants or products in a reaction at equilibrium will cause the system to adjust itself to restore a new equilibrium, affecting the rate of the forward and reverse reactions accordingly.