determine the electrochemical potential and the free-energy change for a system where a solution of 0.1 m mn2 at ph 1 is shaken in air at 0.2 bar pressure of o2, resulting in production of mno2 (s), with the reduction of the oxygen to water. if the ph is held constant at 1 and the oxygen pressure at 0.2 bar, what will be the equilibrium concentration of mn2 in the presence of excess mno2