JEE Main · 2021 · 18 Mar 2021 · Shift 2 · General Principles and Processes of Isolation of Metals

Mercury boils at $630$ K, far below the metals that contaminate it, so it is freed from them by distilling it off and condensing the vapour. Blister copper is cast as the anode of an electrolytic cell and redeposited pure at the cathode, the noble impurities settling as anode mud. Silicon for semiconductor use needs a purity far beyond chemical methods, and zone refining supplies it by moving a molten band along the rod, since the impurities are more soluble in the melt than in the solid and are swept to one end. Nickel combines with carbon monoxide at about $330$ K to give volatile $\mathrm{Ni}(\mathrm{CO}{)}_4$, which decomposes at about $450$ K to leave the pure metal, a vapour phase process. Mercury goes with distillation refining, copper with electrolytic refining, silicon with zone refining and nickel with vapour phase refining.