In electrolysis of water with inert electrodes in acidic solution, what are the products at the cathode and anode respectively?

• A. Cathode: O2; Anode: H2
• B. Cathode: H2; Anode: O2
• C. Cathode: H2O; Anode: O2
• D. Cathode: H2; Anode: H2

Answer: (B)

In electrolysis of water with inert electrodes in acidic solution, you drive reduction at the cathode and oxidation at the anode, using the species present: H+ from the acid and water. At the cathode, H+ gains electrons to form hydrogen gas: 2H+ + 2e- → H2. At the anode, water is oxidized to oxygen gas, releasing protons and electrons: 2H2O → O2 + 4H+ + 4e-. Balancing electrons gives the overall reaction: 2H2O → 2H2 + O2. So the cathode produces hydrogen, and the anode produces oxygen.