Electrolysis of water

Water decomposes to hydrogen and oxygen under electric current


Electrolysis of Water

The Sci Guys: Science at Home - SE1 - EP1: Electrolysis of Water

by The Sci Guys

Электролиз воды

Electrolysis of Water Setup

by John Biegun

Water Electrolysis

by sciencefix

Electrolysis of Water H2O Lab Version

by MortimerCCScience

Electrolysis of Water

by Ray Venables


Wear lab gloves and eye protection. Follow the safety instructions when deal with current.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

2 H2O -[DC]→ 2 H2 + O2


  1. Water

Step-by-step instruction

  1. Fill an electrolysis cell with water.
  2. Fill two test-tubes with water.
  3. Put the test tubes on the electrodes so that water doesn't pour out of the test-tubes.
  4. Switch on a DC power supply. Gases begin evolving on the electrodes.

Scientific background

Water decomposes to hydrogen and oxygen under an electric current. Hydrogen gas is produced on the cathode, oxygen gas is produced on the anode. Following the stoichiometry of this reaction, the amount of hydrogen is twice more than amount of oxygen. This is demonstrated by comparing the volumes of produced gases - the volume of hydrogen is twice more than the volume of oxygen.

To increase the conductivity of water, you may add a salt formed from active metal cations and an oxyacid anion (anions).


Published on 09 September 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst