Products of Electrolysis of Sodium Chloride

Remember 9.1 Practical Skills Practical Skills


  1. Prepare one beaker of dilute sodium chloride solution and one beaker of concentrated sodium chloride solution.
  2. Set up two electrolytic cells using two beakers. A current should be run through the beakers on at a time.
  3. Place a test tube at both electrodes, taking care to trap any gas formed during the reaction.
  4. Place a pH meter at both the electrodes of the dilute sodium chloride solution.
  5. Light a splint, gently blow it out, and place near each of the two electrodes in the dilute sodium chloride solution beaker in quick succession.
  6. Repeat steps 3 to 5 for the beaker containing the concentrated sodium chloride solution.
  7. Waft (ideally, conduct the experiment in a fume cupboard) any gases formed during the experiment carefully towards yourself to identify its contents.
  8. Place a piece of litmus paper each at both electrodes of the concentrated sodium chloride solution.

Expected Results:

  • The pH was below 7 at the anode, and above 7 at the cathode. This indicates the self-ionisation of water brought about by the unresponsiveness of sodium ions to reduction where water is present.
  • A re-lighted splint indicates the presence of oxygen.
  • A popping sound produced when gas caught in a test tube is ignited indicates the presence of hydrogen gas.
  • Chloride gas has a distinct odour which is immediately identifiable.
  • The bleaching of litmus paper at the anode of the concentrated sodium chloride solution confirms the presence of chloride gas.