Pt(s) | Sn2+ (aq, 1 M), Sn4+ (aq, 1 M) || Fe2+ (aq, 1 M), Fe3+ (aq, 1 M) | Pt(s) Anode reaction is:
Fe2+ → Fe3+ + 1e–
Pt → Pt2+ + 2e–
Sn2+ → Sn4+ + 2e–
Pt → Sn2+ + 2e–
The oxidation half reaction for following reaction is Fe2+(aq) + Cr2O72-(aq) → Fe3+ (aq) + Cr3+(aq)