Changing the concentration of reactants or products 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 rate will increase to consume the excess reactants and produce more products, shifting the equilibrium to the right. Conversely, if the concentration of products is increased, the reaction rate will increase in the reverse direction to consume the excess products and produce more reactants, shifting the equilibrium to the left.Similarly, if the concentration of reactants is decreased, the reaction rate will decrease, and the system will shift to the left to produce more reactants. If the concentration of products is decreased, the reaction rate will decrease in the reverse direction, and the system will shift to the right to produce more products.In summary, changing the concentration of reactants or products at equilibrium will cause the system to adjust the reaction rate and shift the equilibrium position to counteract the change and restore a new equilibrium state.