JEE Main · 2021 · 24 Feb 2021 · Shift 1 · General Principles and Processes of Isolation of Metals

Which of the following ore is concentrated using group 1 cyanide salt ?

(A)Sphalerite✓ Correct
(B)Siderite
(C)Malachite
(D)Calamine

Answer: (A)

Solution

Sphalerite (ZnS) is concentrated using cyanide salt as a depressant to remove the impurity of galena (PbS). The reaction is:

ZnS + PbS + excess NaCN ⟶ solution Na_{2} [Zn (CN)_{4}] + PbS

The zinc sulfide forms a soluble complex with cyanide ions, while lead sulfide remains as a solid and can be separated. This is a froth flotation process where NaCN acts as a depressant for ZnS, preventing it from floating so that PbS can be selectively floated and removed.

JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Single correct option

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