Difficulties Encountered During Extraction Of Alkali Metals

S and P Block Elements of Class 11

Difficulties Encountered During Extraction Of Alkali Metals

Alkali metals, can not be extracted from their ores by the usual methods of extraction of metals because of the following difficulties:

  1. Alkali metals are strong reducing agents and hence can not be extracted by reduction of their oxides or chlorides.
  2. Alkali metals being highly electropositive can not be displaced from the aqueous solutions of their salts by other metals.
  3. Alkali metals can not be isolated by electrolysis of the aqueous solution of their salts since hydrogen is liberated at the cathode instead of the alkali metal because the discharge potentials of alkali metals are much higher than that of the hydrogen. However, by using mercury as cathode, the alkali metals can be deposited at the cathode but the alkali metals so deposited readily combines with mercury to form an amalgam from which its recovery is very difficult.

Therefore in view of above difficulties, only successful method is the electrolysis of their molten (fused) salts usually chlorides.

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