Question

Write briefly about the three methods of electrolysis of sodium chloride

Answer 1

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Electrolysis of sodium chloride solution with inert electrodes can be done in several different ways, producing different sets of products.

* Solid sodium chloride melts at just over 800oC, and electrolysis of molten sodium chloride yields sodium metal at the cathode and chlorine gas at the anode.

* Concentrated aqueous sodium chloride solution with a mercury cathode produces a solution of sodium metal in mercury ("sodium amalgam") and chlorine at the anode.

* Dilute aqueous sodium chloride solution produces hydrogen at the cathode and oxygen at the anode.

* Concentrated aqueous sodium chloride solution produces hydrogen at the cathode and chlorine at the anode.

* Aqueous solutions of intermediate concentrations may produce both chlorine and oxygen at the anode.

Sodium metal and chlorine gas can be obtained with the electrolysis of molten sodium chloride.Electrolysis of aqueous sodium chloride yields hydrogen and chlorine, with aqueous sodium hydroxide remaining in solution.The reason for the difference is that the reduction of Na+ (E° = –2.7 v) is energetically more difficult than the reduction of water (–1.23 v).

Terms : anodeThe electrode of an electrochemical cell at which oxidation occurs.cathodeThe electrode of an electrochemical cell at which reduction occurs.