Question

The electrolytic reduction technique is used in the extraction of:

Answer 1

Hint :Electrolytic reduction is a form of electrolysis in which electric current passes through an ionic substance in a molten or dissolved state causing the electrodes to react chemically and the materials to decompose. By using this process, the hydroxides, oxides and chlorides of metals in the combined state are electrically reduced. The metals are collected at the cathode.

Complete Step By Step Answer:
The type of extraction method to be used for the extraction of the metals from their ores depends upon its position in the reactivity series. Metals that lie below the carbon in the reactivity series can be extracted from their respective oxides by heating them with carbon. In this reaction, carbon gets oxidized to carbon dioxide while the metal oxide gets reduced to its respective metal. Such metals include Zinc, Iron, lead, tin and Copper.
But for the metals that lie above carbon in the reactivity series, their respective oxides cannot be reduced by heating it with $ C{O_2} $ . Oxides of strong electropositive metals such as $ K,{\text{ }}Ca,{\text{ }}Na,{\text{ }}Al{\text{ }}and{\text{ }}Mg $ are very stable. It is difficult to reduce them into metallic states by simple carbon reduction. Hence, chlorides/oxides/ hydroxides of such metals are extracted by passing electricity through them.
For example: Sodium is extracted by electrolytic reduction of molten sodium chloride. When the current is passed through fused sodium chloride, sodium ion is reduced at the cathode while chloride ions are oxidised at the anode. The chemical reactions are given below:
 $ At{\text{ }}cathode:{\text{ }}N{a^ + } + {e^ - } \to Na\left( s \right) $
 $ At{\text{ }}anode:{\text{ }}Cl \to \dfrac{1}{2}C{l_2}\left( g \right) + {e^ - } $
So we can say that electrolytic extraction technique is used in extraction of highly electropositive metals.

Note :
Among all the elements of the periodic table, the alkali metals are considered to be the most electropositive. Alkali and alkaline earth metals are generally going to be purified by using electrolytic reduction in the electrolytic method; the source of the potential electrons or current is from outside. So that reduction can be done easily.