Question

The reagent(s) that can selectively precipitate S²⁻ from a mixture of S²⁻ and \[\ce{SO^{2-}_4}\] in aqueous solution is (are) ______.

Options

• CuCl₂

• BaCl₂

• Pb(OOCCH₃)₂

• Na₂[Fe(CN)₅NO]

Answer 1

The reagent(s) that can selectively precipitate S²⁻ from a mixture of S²⁻ and \[\ce{SO^{2-}_4}\] in aqueous solution is (are) BaCl₂.

Explanation:

CuCl₂ can selectively precipitate S²⁻ ions as CuS because CuS is highly insoluble, whereas it does not precipitate \[\ce{SO^{2-}_4}\] ions as copper sulphate is soluble in water. Other reagents like BaCl₂ precipitate \[\ce{SO^{2-}_4}\] as BaSO₄, not S²⁻. Thus, CuCl₂ is used to selectively remove S²⁻ from a mixture containing \[\ce{SO^{2-}_4}\] ions.