A) Balance the one-electron reduction half-reaction of SO42- (aq)/H2S (g) under acidic conditions.

b) Write down the expression of pE in terms of pH, concentration of SO42- (aq), and partial pressure of H2S (g), given that pE = -3.50 when pH = 7.00 and all concentrations and pressures are standard.

c) Deduce the partial pressure of hydrogen sulfide in bars when the sulfate ion concentration is 10-5 M and the pH is 6.0 for water in equilibrium with atmospheric oxygen (where oxygen is the dominant redox species). Henrys Law constant, KH(O2) = 1.3 x 10-3 M atm-1.