Electrolysis of aluminium oxide

• Electrolysis


  Used to extract some metals
• Extracting aluminium by electrolysis

  1. Mix aluminium oxide with compound cryolite to lower melting point

  2. Apply electric current to molten aluminium oxide

  3. Aluminium ions attracted to cathode and gain 3 electrons to form aluminium atoms

  4. Oxide ions attracted to anode and lose 2 electrons to form oxygen atoms
• Half equation for cathode reaction

  Al3+ + 3e- → Al
• Half equation for anode reaction

  2O2- → O2 + 4e-
• Oxygen atoms formed at anode pair up to form oxygen molecules O2
• Anode must be replaced regularly as the oxygen reacts with the graphite to form carbon dioxide
• Extracting metals by electrolysis

  • Requires a lot of energy to melt the compounds
  • Requires a lot of energy to produce the electric current