Question

For the given aqueous reaction which of the statcment(s) is (are) true?
Excess $KI + K_3[Fe(CN)_6 \xrightarrow{\text{Dilute}} H_2SO_4 $

• A. The first reaction is a redox reaction
• B. White precipitate is $Zn_3[Fe(CN)_6]_2$
• C. Addition of filtrate to starch solution gives blue colour
• D. White precipitate is soluble in $NaOH$ solution

Answer 1

Answer: (A), (C), (D)

$K_{3}\left[\overset{+3}{F e}(C N)_{6}\right]+K I($ excess $) \longrightarrow K_{4}\left[\overset{+2}{F e}(C N)_{6}\right]+\underset{\text{Brownish yellow solution}}{K I_{3}\text{(redox)}}$
$K_{4}\left[F e(C N)_{6}\right]+Z n S O_{4} \longrightarrow K_{2} Z n_{3}\left[F e(C N)_{6}\right]_{2}$ or $\underset{\text{White ppt}}{K_{2} Z n\left[F e(C N)_{6}\right]}$
$\underset{\text{Brownish yellow filtrate}}{I_{3}^{-}} +2 N a_{2} S_{2} O_{3} \longrightarrow \underset{\text{Clear solution}}{N a_{2} S_{4} O_{6}}+2 N a l+ \underset{\text{(Turns starch solution blue)}}{I_{2}}$
$K_{2} Z n\left[F e(C N)_{6}\right]$ reacts with $NaOH$ as
$K_{2} Z n\left[F e(C N)_{6}\right]+N a O H \longrightarrow\left[Z n(O H)_{4}\right]^{2-}+\left[F e(C N)_{6}\right]^{4-}$