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1)

The reagent(s)  that can selectively precipitate S2  from a mixture of  S2 and  SO24 in aqueus  solution is (are)


A) CuCl2

B) BaCl2

C) Pb(OOCCH3)2

D) Na2[Fe(CN)5NO]

Answer:

Option A

Explanation:

S2+CuCl2CuS  (black ppt.)

SO24+CuCl2Soluble, thus

   (a)  CuCl2 selectively precipitates  S2

   (b)    S2(soluble)+BaCl2BaS

          SO24(whiteppt.)+BaCl2BaSO4

(b)   precipitates    SO24  and not  S2

 (c) S2(black.ppt)+Pb2+PbS

     SO24(white.ppt)+Pb2+PbSO4

  S2 and    SO24, both are precipitated.

  (d)     S2+Na2[Fe(CN)]5NONa4[Fe(CN)]5NOS]

                             Sodium nitroprusside                          (purple colour)

 But no colour with  SO24