Predict the standard potential (E°) of the galvanic cells

Question

Predict the standard potential (E°) of the galvanic cells with the following cell reactions:

           

a)   3 V2+(aq) + 2 U°(s) → 2 U3+(aq) + 3 V°

 

b)   Sn2+(aq) + Pb4+(aq) → Sn4+(aq) + Pb2+(aq)

Answer 1

a) V²⁺ + 2e- ==> V(s) Eº = -1.18 V

U³⁺ + 3e- ===> U(s) Eº = -1.79 V

Reduction at cathode is V²⁺ + 2e- ==> V(s) Eº = -1.18 V

Oxidation at anode is U(s) ===> U³⁺ + 3e- Eº = -1.79

Eºcell = cathode - anode = -1.18 - (-1.79)

Eºcell = 0.61 V

b) Sn⁴⁺ + 2e- ===> Sn²⁺ Eº = +0.15 V

Pb⁴⁺ + 2e- ===> Pb²⁺ Eº = +1.67 V

Reduction at cathode is Pb⁴⁺ + 2e- ===> Pb²⁺ Eº = +1.67 V

Oxidation at anode is Pb²⁺ ===> Pb⁴⁺ + 2e- Eº = +0.15 V

Eºcell = cathode - anode = 1.67 - 0.15

Eºcell = 1.52 V