Nernst Equation
Ecell = cell potential under non-standard conditions
E°cell = standard cell potential
n = mole e- transferred
Q = reaction quotient = products/reactants
Step 1: Identify the anode and the cathode in the reaction and write the overall reaction
• ↓ E° → oxidation → anode
• ↑ E° → reduction → cathode
Cu2+ + 2 e- → Cu E° = 0.3419 V → cathode
Zn2+ + 2 e- → Zn E° = – 0.7618 V → anode
lose electrons → oxidation → anode
gain electrons → reduction → cathode
Balance the electrons:
Cathode: Cu2+ + 2 e- → Cu
Anode: Zn → Zn2+ + 2 e-
Overall reaction: Cu2+ + Zn → Cu + Zn2+
# of electrons transferred = 2 e-
Step 2: Calculate the cell potential of the reaction.
Cu2+ + 2 e- → Cu E° = 0.3419 V → cathode
Zn2+ + 2 e- → Zn E° = – 0.7618 V → anode
E°cell = 1.1037 V
Step 3: Calculate Ecell using the Nernst Equation.
What will be the cell potential for a Cu−Zn galvanic cell with [Zn2+] = 0.1 M and the [Cu2+] = 0.01 M?
a) 1.10 V
b) 1.13 V
c) 1.04 V
d) 1.07 V
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