Electrolysis

• Equipment

  • Beaker for electrolyte (liquid that contains an ionic compound that can conduct electricity)
  • Electrodes- solid conductors generally made with metal or carbon
  • On the right is the positive anode
  • On the left is the negative cathode
  • Join electrodes with wire so that electrons can flow between them
  • Add a power supply (such a battery) to drive flow of electrons
• Electrolysis means splitting up electricity (the electrolyte is Lead Bromide)

  • Negative (bromide) ions will be attracted to the positive anode, and will be discharged. The ions are being oxidised.
  • Forms a gas and escapes
  • Positive (lead) ions will attracted to the negative cathode and also be discharged. The ions are being reduced.
  • Sinks to bottom as pure Lead
  • Electrons from bromide ions are being taken by the anode and transported to the cathode by the power of the battery. Then these electrons are given to the positive led ions to from neutral ions.
• Electrolysis is expensive because it requires a lot of energy
• Electrolysis only works if the ions can move.
• How to extract metals from ore (Aluminium as example)

  • Purify aluminium oxide from bauxite ore
  • Melt aluminium oxide to make it molten
  • Mix it with cryolite to lower the melting point
  • Melting temperature is lower but still really high, so uses loads of energy.
  • Now you have molten aluminium oxide.
• Anode

  O^2- --> O2 + 2e-
• Cathode

  Al^+3 + 3e- --> Al
• Electrolysis equation

  Al2+O3 --> Al + O2
• Soluble compounds can just be dissolved in water to form an electrolyte
• Electrolysis in an aqueous solution

  • As well as the negative and positive ions there is also hydrogen and hydroxide ions
• The ion of the least reactive element will be discharged first at the cathode.
• At the anode if a halide is present then it will be discharged but if not the hydroxide will always be discharged.
• Copper will accumulate around cathode in electrolysis.