Increasing the pH of a solution containing the redox system Fe2+/Fe3+ will affect the equilibrium concentration of Fe2+ at 25C. The redox reaction between Fe2+ and Fe3+ can be represented as:Fe3+ + e- Fe2+When the pH of the solution increases, the concentration of H+ ions decreases. The Fe3+ ions can react with the OH- ions from the increased pH to form Fe OH 3, which is a precipitate:Fe3+ + 3OH- Fe OH 3 s This reaction removes Fe3+ ions from the solution, which shifts the redox equilibrium to the left according to Le Chatelier's principle. As a result, the equilibrium concentration of Fe2+ will increase in response to the increased pH.