In a galvanic cell with E°(Cu2+/Cu) = +0.34 V and E°(Zn2+/Zn) = −0.76 V, which electrode is the cathode?

• A. Copper electrode
• B. Zinc electrode
• C. Hydrogen electrode
• D. Silver electrode

Answer: (A)

In a galvanic cell, the cathode is where reduction occurs, and it’s the half-reaction with the more positive standard reduction potential. Here, the copper couple Cu2+/Cu has E° = +0.34 V, while Zn2+/Zn has E° = −0.76 V. Since +0.34 V is more positive, the reduction at the cathode will be Cu2+ + 2e− → Cu. The zinc electrode thus serves as the anode, where oxidation occurs (Zn → Zn2+ + 2e−). Therefore, the copper electrode is the cathode. The hydrogen electrode and the silver electrode aren’t involved in this cell given these potentials.