Introduction
Electrolysis of a molten salt, such as sodium chloride, is a process where an electric current passes through a molten salt to form two products - the metal to be extracted and a less readily oxidised component. The process is called double metal electrolysis because, unlike single metal electrolysis, both metal atoms in the salt are extracted. This process has been used extensively in the production of aluminium and magnesium, as well as other metals.
Working Principle and Mechanism
Double metal electrolysis works on a principle known as redox reactions. In a redox reaction, a metal gains electrons, while the other metal loses electrons. This redox reaction then occurs between the two metals in the salt, with electrons passing through the molten salt. As the current flows, metal atoms from the molten salt are reduced at the cathode and the oxidized metal from the metal component is oxidized at the anode. This process continues until both metals are completely discharged. Here, the oxidized metal acts as a cathode and the reduced metal acts as an anode.
Process
The first step in double metal electrolysis is to dissolve the salt in water. This produces a solution of salt containing two dissolved ions. The electrolysis process then begins by passing an electric current through the solutions. As the current passes through the solutions, the two metal ions of the salt are oxidized and reduced, respectively. At the cathode, the reductive reaction occurs and the metal ions are reduced to form metal atoms. At the anode, the oxidizing reaction occurs and the metal ions are oxidized to form metal atoms.
The metal atoms that are formed at the cathode are collected at the bottom of the cell while the metal atoms that are formed at the anode form a layer at the top of the cell. These two layers are then separated and the respective metal atoms are extracted from the solutions. The extracted two metals can be further processed to form products.
Conclusion
Electrolysis of a molten salt is a process used to extract two metals from a single salt. This double metal electrolysis process involves passing an electric current through the salt to form two product – one metal atoms at the cathode and the other at the anode. The metal atoms then reactions with the anode-cathode reactions, with the oxidized metal forming a layer at the top of the cell while the reduced metal form a layer at the bottom of the cell. The two layers are then separated, after which the metals can be further processed to form products.
