(a) Write the principle of electrolytic refining.

(b) Why does copper obtained in the extraction from copper pyrites have a blistered appearance?

(c) What is the role of depressants in the froth floatation process?

(a) Electrolytic refining: Many of metals as Cu, Ag, Au, AL, Pb etc., are purified by this method. Here, the cathode is made up of pure metal and anode is made up of impure metal. The electrolyte used is in fact an aqueous solution of salt of the metal. Thus,

Anode → impure metal

Cathode → Pure metal

Electrolyte → salt of metal in aqueous solution.

(b) The principal ore of copper is copper pyrites [CuFeS₂]. The ore is concentrated by froth flotation process. The molten copper is poured out and allowed to cool. When Sulphur dioxide is trying to escape it gets trapped in the cooler parts of the metal forming blisters on the surface of copper and hence it is called blister copper.

(c) Activators and depressants are the compounds which activate and depress respectively the floating property of one of the components of the ore and thus, help in the separation of different minerals present in the same ore. Copper sulphate is an example of activator, while sodium and potassium cyanides are the examples of depressants.