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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper I covers inorganic chemistry.

UPSC Combined Geo-Scientist, Mains · 2019 · Mains Paper I

Q11(a). Selective sulfide precipitation

Question

At ordinary temperature, the solubility product (Kₛₚ) values of copper and manganese sulphides are as follows: CuS ≃10⁻³⁶; MnS ≃10⁻¹¹. Explain how sulphides are selectively precipitated from the mixture of Cu²⁺ and Mn²⁺ ions.

Answer in brief

Use low sulfide concentration in acid to precipitate CuS while retaining Mn(II); after filtration, raise pH to precipitate MnS.

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CoversSelective sulfide precipitationSolubility equilibria

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