Electrolysis

• Aluminium oxide:

  • extracting metals using electrolysis is expensive because large amounts of energy is needed to melt ore
  • Aluminium oxide is extracted from bauxite
  • Aluminium oxide has high melting point so it is mixed with cryolite to lower melting point
  • Having a high melting point means a lot of energy is needed to heat aluminium oxide to melting point
• at the cathode:

  • Reduction - gain of electrons
  • aluminium attracted to cathode - aluminium gains 3 electrons
  • Aluminium is produced

  Al(3+) + 3e(-) —> Al
• at anode:

  • oxidation
  • negative oxygen ions attracted to anode
  • negative oxygen ions lose two electrons
  • oxygen is produced
• • The anode is made of carbon and needs to be replaced regularly because the carbon anode reacts its oxygen to produce carbon dioxide
• • an ionic solid cannot be ionised because the ions are in fixed positions and cannot move