Question

A reddish brown precipitate is formed by the ions:

• A. $A{g}^{+}andC{l}^{-}$
• B. $C{u}^{2+}and\left[Fe\right(CN{)}_6{]}^{4-}$
• C. $C{d}^{2+}and{S}^{2-}$
• D. Sodium nitroprusside and $N{a}_{2}S$

Answer 1

The correct option is B $C{u}^{2+}and\left[Fe\right(CN{)}_6{]}^{4-}$

$A{g}^{+}+C{l}^{-}\to \underset{white}{AgCl}$

$C{u}^{+2}+\left[Fe\right(CN{)}_6{]}^{4-}\to \underset{Reddishbrownppt}{C{u}_2\left[Fe\right(CN{)}_6]}$
$C{d}^{+2}+S^{-2}\to \underset{yellow}{CdS}$
$N{a}_{2}S$ gives a purple colour with sodium nitroprusside due to the formation of sodium thionitroprusside.