Changing the pH of a redox reaction can affect its equilibrium position by altering the concentrations of the reactants and products involved in the reaction. This is particularly true for redox reactions that involve acidic or basic species. The change in pH can shift the equilibrium position either to the right favoring the formation of products or to the left favoring the formation of reactants .A specific example of a redox reaction that is affected by pH changes is the reduction of iron III ions Fe by iodide ions I in an acidic solution:2Fe aq + 2I aq + 6H aq 2Fe aq + I aq + 3HO l In this reaction, the iron III ions are reduced to iron II ions Fe , and the iodide ions are oxidized to iodine I . The presence of H ions protons in the reaction indicates that the reaction occurs in an acidic environment.If the pH of the solution is increased i.e., the concentration of H ions is decreased , the reaction will shift to the left to counteract the change and produce more H ions. This means that the reduction of Fe ions will be less favorable, and the oxidation of I ions will also be less favorable. Consequently, the equilibrium position will shift towards the reactants, and the concentrations of Fe and I ions will increase, while the concentrations of Fe and I will decrease.On the other hand, if the pH of the solution is decreased i.e., the concentration of H ions is increased , the reaction will shift to the right to counteract the change and consume the excess H ions. This means that the reduction of Fe ions will be more favorable, and the oxidation of I ions will also be more favorable. Consequently, the equilibrium position will shift towards the products, and the concentrations of Fe and I will increase, while the concentrations of Fe and I ions will decrease.In summary, changing the pH of a redox reaction can significantly affect its equilibrium position, particularly for reactions that involve acidic or basic species. In the case of the reduction of iron III ions by iodide ions, increasing the pH shifts the equilibrium position towards the reactants, while decreasing the pH shifts the equilibrium position towards the products.