The balanced redox reaction should be: MnO4-(aq) + 5Fe^2+(aq) + 8 H+(aq) --> Mn^2+(aq) + 5Fe^3+(aq) + 4H2O(l).
As for the galvanic cell, we know our cathode and our anode from the balanced half-reactions:
nicole-2B wrote:a) MnO4-(aq) +8H+(aq)+5e- yields Mn2+(aq) +4H2O (cathode half reaction)
5[Fe2+ (aq) yields Fe3+(aq)+e-] (anode half reaction)
Since neither half-reaction involves a species in its solid state, include a platinum electrode (Pt) in each half-cell. Separate species in the same phase by commas and exclude H2O(l):
Pt(s)|Fe^2+(aq), Fe^3+(aq)||MnO4-(aq), H+(aq), Mn^2+(aq)|Pt(s)