Electrolysis

• Anode - positive electrode

  • attracts negative ions
  • oxidation at the anode (ions lose electrons)
• Cathode - negative electrode

  • attracts positive ions (Cat attract pawsitive)
  • Reducation at the cathode (ions gain electrons)
• Cathode

  Al2O3, Aluminium Oxide

  • product = aluminium
  • Half equation = Al (+3) +3e (-1) -> Al
• Anode

  Al2O3, Aluminium Oxide

  • Product = Oxygen
  • Half equation = 2O (-2) -> O2 + 4e (-1)
• In aqueous solutions:

  • If H+ ions and metals ions are present, hydrogen gas will be produced if the metal is more reactive than hydrogen
  • If the metal is less reactive than hydrogen, a solid layer of pure metal is produced instead
• In aqueous solution:

  • If halide ions are present at the anode, molecules of the halide ion will be produced
  • If no halide ions are present, then Oxygen will be formed from the hydroxide ions
• In aqueous solution, aswell as the ions from the ionic compound, Hydrogen ions (H+) and Hydroxide ions (OH-) will be present from the water.

  • H2O -> H + OH
• Non-inert electrodes can decompose into the electrolyte.

  Eg. Copper electrodes in a solution of copper sulfate
• Non-inert electrodes

  • Mass of cathode increases
  • Mass of anode decreases

  This is because copper is transferred from the anode to the cathode
• Non-inert electrodes half equations:

  Anode:

  Cu (s) -> Cu (+2) (aq) + 2e (-1)

  Cathode

  Cu (+2)(aq) + 2e (-1) -> Cu (s)