Passing current through molten NaCl yields sodium at the cathode and chlorine at the anode.
Practise Acids, Bases & Electrochemistry All Acids, Bases & Electrochemistry topics
In molten salts there is no water to compete for discharge, so cations are reduced at the cathode and anions are oxidized at the anode. Molten sodium chloride, for example, yields sodium metal at the cathode and chlorine gas at the anode when a current is passed. This is the principal industrial route to highly reactive metals such as sodium, magnesium and aluminium, which cannot be obtained from aqueous solution. Other salts are often added to lower the melting point, and the process is energy intensive. It demonstrates electrolysis in its simplest form.
Key ideas: With no water present, ions are the only species to be discharged. For molten NaCl: cathode 2Na+ + 2e- giving 2Na, anode 2Cl- giving Cl2 + 2e-. Used for Na, K, Mg (from MgCl2), Ca and Al. A flux such as CaCl2 lowers the melting temperature of NaCl from 801 C to about 600 C.
Common mistakes and connections: Mistake: applying aqueous rules (such as H2 at the cathode) to molten systems. Products from molten salts are predictable: metal at the cathode, nonmetal at the anode. Liquid sodium must be kept from air and water. Compare with aqueous electrolysis, where water often competes.
With no water present, molten NaCl is simply split: sodium forms at the cathode and chlorine at the anode in the Downs cell. The interactive lesson shows this as a live animation or chart.
The Downs cell electrolyzes molten sodium chloride to produce sodium metal and chlorine gas.
Passing current through molten NaCl yields sodium at the cathode and chlorine at the anode.
Electrolysis of Molten Salts is a intermediate topic in Acids, Bases & Electrochemistry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Acids, Bases & Electrochemistry first: Faraday's Constant, Faraday's First Law, Faraday's Second Law.
The next topics in Acids, Bases & Electrochemistry are Electrolysis of Aqueous Solutions and Electroplating.
Yes. The interactive lesson includes a self-check question on Electrolysis of Molten Salts, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Electrolysis of Molten Salts is topic 62 of 105 in Acids, Bases & Electrochemistry.