In the galvanic cell described, which half-reaction occurs at the anode?

• A. Cu2+ + 2 e− → Cu(s)
• B. Cu(s) → Cu2+ + 2 e−
• C. Zn2+ + 2 e− → Zn(s)
• D. Zn(s) → Zn2+ + 2 e−

Answer: (D)

In a galvanic cell, the anode is where oxidation occurs, so electrons are produced there and flow to the cathode. Zinc metal oxidizes readily, so the half-reaction at the anode is Zn(s) → Zn2+ + 2 e−. The electrons then travel to the cathode, where Cu2+ is reduced to Cu(s). The overall cell reaction is Zn(s) + Cu2+ → Zn2+ + Cu(s). The other half-reactions involve reduction of Cu2+ or oxidation of copper metal, which would not place oxidation at the zinc anode in this cell.