Which option is Correct

Question

In the metallurgy of sulphide ores which also contain other sulphide impurities, depressants are added  to selectively allow the ore particles to come to froth while the sulphide impurity remains in solution. Suppose we have a mixture of Galena and Zinc and NaCN is added. Select the correct option:

(1)  PbS comes to froth whereas zinc froth whereas zinc forms a complex [Zn(CN)₄]^2- 

(2) PbS comes to froth whereas zinc forms a complex [Zn(CN)₆]^4- 

(3) ZnS comes to froth whereas lead forms a complex  [Pb(CN)₄]^2-

(4) ZnS comes to froth whereas lead forms a complex [Pb(CN)₆]^2-

Answer 1

Answer (1)

CN^– ions have greater affinity for zinc and ZnS is retained in solution as Zn (CN)₄^2–