Changing the pH of the solution will affect the concentration of H+ ions, which are involved in the redox reaction: Fe2+ + 2H+ Fe3+ + H2O. According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust the equilibrium position to counteract the change.In this case, if the pH is decreased meaning an increase in H+ ion concentration , the reaction will shift to the right to consume the excess H+ ions. This will result in an increase in the concentration of Fe3+ ions and a decrease in the concentration of Fe2+ ions.On the other hand, if the pH is increased meaning a decrease in H+ ion concentration , the reaction will shift to the left to produce more H+ ions. This will result in a decrease in the concentration of Fe3+ ions and an increase in the concentration of Fe2+ ions.In summary, changing the pH of the solution will affect the equilibrium position of the redox reaction by shifting it either to the right or left, depending on whether the pH is decreased or increased, respectively.