An aqueous solution of a salt $X$ turns blood red on treatment with CNS $^{-}$ and blue on treatment with…

An aqueous solution of a salt $X$ turns blood red on treatment with CNS $^{-}$ and blue on treatment with $\mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight] . \mathrm{X}$ also gives a positive chromyl chloride test. The salt $X$ is :
  1. $\mathrm{CuCl}_{2}$
  2. $\mathrm{FeCl}_{3}$
  3. $\mathrm{Cu}\left(\mathrm{NO}_{3}ight)_{2}$
  4. $\mathrm{Fe}\left(\mathrm{NO}_{3}ight)_{3}$

Solution

$\mathrm{Fe}^{3+}$, radical gives blood red with $\mathrm{CNS}^{-}$
$\mathrm{Fe}^{3+}+3 \mathrm{CNS}^{-} \longrightarrow \mathrm{Fe}(\mathrm{CNS})_{3}$
Ferric sulphocyanide (Blood red colouration) $\mathrm{Fe}^{3+}$ gives blue colour on treatment with $\mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight]$
$4 \mathrm{Fe}^{3+}+3 \mathrm{~K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight] \longrightarrow$
$12 \mathrm{~K}^{+}+\mathrm{Fe}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight]_{3}$
Ferricferrocyanide (Prussian blue) $\mathrm{Cl}^{-}$ radical gives chromyl chloride test.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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