Exercise 9 | Electrochemistry

Here is a galvanic cell: Zn (s) | Zn2+ (aq) || Cd2+ (aq) | Cd (s)

Write the cell equation and calculate E0cell, ΔGrxn and Ecell at 25°C.


Data: [Zn2+] = 1.00 x 10-2M

[Cd2+] = 2.00 x 10-2 M

E0red (Zn2+/Zn) = - 0.762 V

E0red (Cd2+/Cd) = - 0.403 V

Zn (s) → Zn2+ (aq) + 2 e-

Cd2+ (aq) + 2 e- → Cd (s)

cell equation: Zn(s) + Cd2+ (aq) → Zn2+ (aq) + Cd (s)

 

E0cell = E0reduction + E0oxidation

E0cell = E0red (Cd2+/Cd) - E0red (Zn2+/Zn)

E0cell = - 0.403 + 0.762

E0cell = 0.359 V

 

ΔG0rxn = - νeFE0cell

ΔG0rxn = - 2 x 96485 x 0.359

ΔG0rxn = - 69.3 kJ.mol-1

 

ΔGrxn = ΔG0rxn + RT ln Q

ΔGrxn = - 69.3 x 103 + 293 x 8.314 x ln 10-22 × 10-2

ΔGrxn = - 71.0 kJ.mol-1

 

Ecell = - GrxnνeF

Ecell = 71.0 × 1032 × 96485

Ecell = 0.368 V