The reaction between iodide ion I and persulfate ion S2O8 can be represented by the following equation:2 I aq + S2O8 aq 2 IO aq + 2 SO4 aq This reaction is governed by the principles of chemical equilibrium, which can be described by the equilibrium constant K . The equilibrium constant is the ratio of the concentrations of products to reactants, each raised to the power of their stoichiometric coefficients.K = [IO][SO4] / [I][S2O8] Now, let's consider the effect of changing the concentration of a reactant or a product on the reaction rate at equilibrium.1. Increasing the concentration of a reactant I or S2O8 : According to Le Chatelier's principle, when a system at equilibrium is subjected to a change in concentration, the system will adjust itself to counteract the change and re-establish equilibrium. In this case, increasing the concentration of a reactant will shift the equilibrium to the right, favoring the formation of products. This will result in an increase in the reaction rate until a new equilibrium is established.2. Decreasing the concentration of a reactant I or S2O8 : Similarly, if the concentration of a reactant is decreased, the equilibrium will shift to the left, favoring the formation of reactants. This will result in a decrease in the reaction rate until a new equilibrium is established.3. Increasing the concentration of a product IO or SO4 : If the concentration of a product is increased, the equilibrium will shift to the left, favoring the formation of reactants. This will result in a decrease in the reaction rate until a new equilibrium is established.4. Decreasing the concentration of a product IO or SO4 : Conversely, if the concentration of a product is decreased, the equilibrium will shift to the right, favoring the formation of products. This will result in an increase in the reaction rate until a new equilibrium is established.In summary, changing the concentration of a reactant or a product will affect the reaction rate at equilibrium for the reaction between iodide ion and persulfate ion. The system will adjust itself according to Le Chatelier's principle to re-establish equilibrium, which may result in an increase or decrease in the reaction rate depending on the specific change in concentration.