Electrolysis of Water
Split water into hydrogen and oxygen and watch the bubbles collect in a 2:1 ratio.
Cathode (−), reduction: 2 H₂O + 2 e− → H₂ + 2 OH−
Anode (+), oxidation: 2 H₂O → O₂ + 4 H+ + 4 e−
Overall: 2 H₂O → 2 H₂ + O₂
Anode (+), oxidation: 2 H₂O → O₂ + 4 H+ + 4 e−
Overall: 2 H₂O → 2 H₂ + O₂
Current0 A
Hydrogen (H₂)0 mL
Oxygen (O₂)0 mL
H₂ : O₂ ratio–
StatusOff
What you can learn
- Electrolysis uses electrical energy to force a non-spontaneous reaction.
- At the cathode water is reduced to H₂, and at the anode it is oxidised to O₂.
- Twice as much hydrogen gas forms as oxygen: 2 H₂O → 2 H₂ + O₂.
Frequently asked questions
Why is there twice as much hydrogen as oxygen?
Water is H₂O, so splitting 2 H₂O gives 4 hydrogen atoms (2 H₂) and 2 oxygen atoms (1 O₂). Equal amounts of gas means twice the volume of hydrogen.
What is the difference between a galvanic and an electrolytic cell?
A galvanic cell makes electricity from a spontaneous reaction. An electrolytic cell uses electricity to force a non-spontaneous reaction.