During the electrolysis of water:
The overall balanced equation for the process is:
2H2O(l) → 2H2(g) + O2(g)
The volume of hydrogen given off is twice the volume of oxygen given off.
The ions compete at each electrode to gain or lose electrons.
Whether hydrogen or a metal is produced at the cathode depends on the position of the metal in the metal reactivity series:
Either oxygen or a non-metal from the electrolyte can be produced at the anode:
The table summarises the product formed at the anode during the electrolysis of different electrolytes in solution.
|Negative ion||Element given off at anode|
|Chloride, Cl-||Chlorine, Cl2|
|Bromide, Br-||Bromine, Br2|
|Iodide, I-||Iodine, I2|
|Sulfate, SO42-||Oxygen, O2|
Chlorine will be produced.
Predict the product formed at the positive electrode during the electrolysis of concentrated sodium sulfate solution.
Oxygen will be produced.