Here's why:
* Electrolysis: This process uses electricity to drive non-spontaneous chemical reactions.
* Cathode: The negative electrode where reduction (gain of electrons) occurs.
* Anode: The positive electrode where oxidation (loss of electrons) occurs.
In brine electrolysis, the following reactions occur:
* At the cathode (reduction):
* 2H2O(l) + 2e- → H2(g) + 2OH-(aq)
* Na+(aq) + e- → Na(s)
* At the anode (oxidation):
* 2Cl-(aq) → Cl2(g) + 2e-
While both reactions are possible at the cathode, the reduction of water is favored due to its lower standard reduction potential. However, the presence of a mercury cathode can significantly lower the reduction potential of sodium ions, making them the primary species reduced.
Therefore, sodium ions are reduced to sodium metal at the cathode during electrolysis of brine, specifically when a mercury cathode is used.
