Refining & Reduction of Crude Metal, Flux and Refractory materials - Free

In this process the finely divided powdered argentite or the native silver or gold is treated with a dilute solution (0.5%) of sodium or potassium cyanide while a current of air is continuously passed. As a result silver pass into solution forming their respective soluble complex cyanides while the impurities remain unaffected which are filtered off.

(A) The Mond process, sometimes known as the carbonyl process, is a technique created by Ludwig Mond in 1890, to extract and purify nickel. Thus, correct match for (A) - (4).
(B) van Arkel method is used for refining zirconium or titanium. In this method, oxygen and nitrogen, present as impurity are removed by heating metal in an evacuated vessel with iodine. Thus, correct match for (B) - (3).
(C) Zone refining is a very useful method to get metals with very high purity such as silicon and germanium. Thus, correct match for (c)-(2).
(D) Many metals, such as copper, zinc, tin, nickel, silver, gold etc. are refined by electrolysis. In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. The solution of the metal salt is used as an electrolyte. Thus, correct match for (D) - (1).
Hence, the correct option is (c).

Electrolysis of cryolite can be explained as

So, the molar ratio of Al and F₂ is 4:6=2:3.