C4.3.5 - Representing Electrolysis as half equations

• Describe and explain what happens are the cathode (negative electrode) and anode (positive electrode) in terms of electrons, oxidation and reduction.

  Reduction happens at the negative cathode because this is where positive ions gain electrons.

  Oxidation happens at the positive anode because this is where negative ions lose electrons.
• Writing half equations for Electrolysis

  A half equation is used to model the reaction that happens at an electrode during electrolysis. It shows what happens when ions gain or lose electrons. In half equations:

  • electrons are shown as e-
  • the numbers of atoms of each element must be the same on both sides
  • the total charge on each side must be the same (usually zero)