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COMEDK2014ChemistryGeneral Principles and Processes of Isolation of Metals

Sodium cyanide is added as a depressant in the froth floatation process when the ore contains a mixture of ZnS and PbS. This is because

Options

  1. APb ( CN )₂ gets precipitated without any effect on ZnS
  2. BZnS forms soluble complex, while PbS forms froth.
  3. CPbS forms soluble complex, while ZnS forms froth.
  4. DZn ( CN ₂ . gets precipitated without any effect on PbS

Correct answer

B. ZnS forms soluble complex, while PbS forms froth.

Step-by-step solution

NaCN forms a soluble complex with ZnS thus, it selectively prevents ZnS from coming to the froth but allows PbS to come with the froth.

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