Electrolysis

• Properties of metals


  • Iron (steel): Strong and hard
  • Aluminium: Strong, low density, good conductor of heat and electricity, resistant to corrosion
  • Copper: Very good conductor of heat and electricity, malleable and ductile, attractive colour and lustre
  • Titanium: Hard, strong, low density, resistant to corrosion, high melting point
• Aluminium Electrolysis


  1. Aluminium oxide dissolves in molten cryolite at a lower temperature

  2. On the cathode: Al + 3e- → Al

  3. On the anode: 2O2- → O2 + 4e-

  4. The oxygen formed reacts with the carbon anodes, forming carbon dioxide gas and requiring anodes to be replaced frequently
• Aluminium Plants


  • Located near the coast to import raw materials
  • Located away from built up areas
  • Located near a town or city to accommodate the workforce
  • Have good transport links for transporting the product to buyers
  • Have a direct electricity supply
• Electrolysis


  The process of breaking down an ionic compound using electrical energy
• Electrolyte


  Liquid which is broken down by an electrical charge
• Electrode


  Graphite rods which carry a current in and out of the electrolyte
• Cathode


  Negative electrode
• Anode


  Positive electrode
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• Electrolysis of water


  1. Hydrogen gas is collected on the cathode

  2. Oxygen gas is collected on the anode

  3. The volume of hydrogen formed is twice the volume of oxygen formed
• Electrolysis of aqueous solutions


  1. Metals lower in the reactivity series than hydrogen are formed on the cathode

  2. For metals higher in the reactivity series than hydrogen, hydrogen gas is formed rather than the metal