A cell is constructed at 298 K based on the reaction below, for which E°cell = 0.81 V. 3 Sn2+(aq) + 2 NO3-(aq) + 8 H+(aq) ---> 3 Sn4+(aq) + 2 NO(g) +4 H2O(l) Calculate the pH in the cathode compartment if the cell emf = 0.67 V when PNO = 1.00 atm, [Sn4+] = 0.10 M, [NO3-] = 0.010 M, and [Sn2+] = 0.020 M