(a) Zinc is refined by electrolysis method. The principle involved in this method is that the impure zinc is made anode while a thin strip of pure zinc is made the cathode, both of them are dipped in a zinc salt solution which acts as electrolyte. When electricity is passed through this circuit, the impure zinc metal at anode gets oxidised and come into the electrolyte
while the zinc ions reduce at cathode to form pure zinc (solid) metal.
(b) (i) It is easy to reduce metal oxides to metals rather than sulphides to metals. Hence sulphide ores are roasted to oxide for easier reduction.
(ii) Carbon has more affinity towards oxygen than Cr2O3 making it a better reducing agent for zinc oxide than Cr2O3.
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