Ferrous sulfate (FeSO4) is often used as a coagulant in water purification. The iron (II) salt is dissolved in the water to be purified, then oxidized to the iron (III) state by dissolved oxygen, at which time gelatinous Fe(OH)3 forms, assuming the pH is above approximately 6. Write balanced chemical equations for the oxidation of Fe2+ to Fe3+ by dissolved oxygen and for the formation of Fe(OH)3 (s) by reaction of Fe3+ with HCO3-(aq).