Which method would you suggest for the separation of the metals in the following mixtures ?
(a) Zinc and iron
(b) Copper and magnesium
(c ) Rare earths
Give reasons for your choice.

Explanation

Zinc and iron : Zinc and iron can be separated from the mixture by fractional distillation. The mixture is distilled, when zinc with low boiling point distils over leaving behind iron.
(ii) Copper and magnesium : Copper and magenesium metals can be separated from the mixture by electrolytic refining. The mixture metal is converted into a rod and made the anode, while a thin thin plate of Pure copper serves as the cathode. The electrolytic tank contains a solution of copper sulphate acidified with dil. `H_(2)SO_(4)`, which acts as the electrolyte on passing electricity. `Cu^(2+)` and thus these `Cu^(2+)` ions are discharged at the cathode as pure metal.
(iii) Rare earths : Rare earths includes lanthanides and actinides. All lanthanide ions are typically trivalent `M^(3+)` and almost identical in size. Their chemical properties. which are determined by the size and charge of their ions, are almost identical. This renders the separation of one metal from another difficult . Different methods employed for their separation given below are based on the light diffenerces in their solubility, stability, and basic properties. Modern methods are based on valence change and ion exchange.
(1) Ion exchange method
(This is a very effective and rapid method)
(2) Complex formation
(3) Solvent extraction
(4) Fractional crystallisation
Valency change method
(5) Thermal reaction
(6) Precipitation.