In the cell Pt | H2 | H+ || Pb2+ | Pb, is the cell galvanic or electrolytic, and what species is produced at the cathode?

• A. Galvanic, H2
• B. Electrolytic, Pb
• C. Galvanic, Pb
• D. Electrolytic, H2

Answer: (B)

Think about which half-reaction would happen spontaneously by looking at standard reduction potentials and who acts as the anode and cathode in the diagram. The left half-cell H2/H+ has a standard reduction potential of 0 V for 2H+ + 2e- → H2, while the right Pb2+/Pb couple has a reduction potential of about -0.13 V for Pb2+ + 2e- → Pb. With the diagram’s left side as the anode (oxidation) and the right side as the cathode (reduction), the overall cell would have a negative cell potential (0 V for the anode minus the cathode value), so the reaction is not spontaneous. That means this setup must be driven by an external power source, i.e., it is electrolytic.

In an electrolytic cell, the cathode is where reduction occurs, so Pb2+ is reduced to Pb at the right-hand electrode. Therefore, Pb metal is produced at the cathode. The left-hand electrode would be oxidized (H2 → 2H+ + 2e−) under the applied voltage.