漂白水發電

The principle of bleaching solution cell is just the same as that of lemon cell. The bleaching solution, which contains mobile Na+(aq), Cl-(aq) and OCl-(aq) ions, acts as an electrolyte in the cell.

To make the cell, a piece of Mg and a piece of Cu are dipped into the bleaching solution and connected by an external circuit. Since Mg is in a higher position in the electrochemical series than Cu, Mg is oxidized to Mg2+(aq) and releases electrons.
Mg(s) → Mg2+(aq) + 2e-

Electrons flow from Mg to Cu in the external circuit. At the Cu electrode, hydrogen ions (not sodium ions) in the electrolyte are reduced (accept electrons) to give hydrogen gas. The reduction of hydrogen ions accepted in HKCE level. However, it has been found that it is water in the electrolyte that undergoes reduction, but not hydrogen ions.
2H+(aq) + 2e- → H2(g)
or : 2H2O(aq) + 2e- → H2(g) + 2OH-(aq)