Question

In an alkaline solution, sodium nitroprusside gives a violet colour with :

• A.
  $S{O}_4^{2-}$
• B.
  $N{O}_2^{-}$
• C.
  $S^{2-}$
• D.
  $C{l}^{-}$

Answer 1

The correct option is C

$S^{2-}$
Sulphide anion is confirmed by treating the alkaline water extract of salt with few drops of sodium nitroprusside solution.
Appearance of purple or violet colouration confirms the presence of sulphide ore.

$S^{2-}+\underset{\text{Sodium nitroprusside}}{N{a}_2\left[Fe\right(CN{)}_{5}NO]}\to \underset{\text{Complex of violet colour}}{N{a}_4\left[Fe\right(CN{)}_{5}NOS]}$