Electrolysis of water

  • Inert platinum or carbon electrodes are used to carry current into and out of the electrolyte.
  • Charged ions carry electric current through an electrolyte and since pure water does not contain many ions some potassium hydroxide or sulphuric acid is added to ionize the water and increase conductivity.

Water is broken into the elements hydrogen and oxygen in the ratios 2 : 1 respectively

  • While current is flowing positive hydrogen (H+) ions migrate
    to the cathode. They accept electrons to form hydrogen atoms, which then combine to form molecules of hydrogen gas. They are discharged as hydrogen gas

  • The negative hydroxide ions (OH) migrate to the anode and give up electrons forming water and oxygen molecules.


Products formed during electrolysis of water

  • Oxygen
  • Hydrogen


Uses of oxygen

  • Manufacture of steel
  • Cutting and welding metals
  • Medical purposes
  • Bleaching agents
  • Used by sea divers and astronauts
  • Making acids e.g. sulphuric acid and nitric acid


Test for Oxygen

  • Insert a glowing splint into oxygen, glowing splint rekindles/relights


Uses of hydrogen

  • Manufacture of ammonia
  • Manufacture of margarine
  • Welding
  • Manufacture fertilisers
  • Fuel

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