JEE MAIN - Chemistry (2025 - 2nd April Morning Shift - No. 6)
Choose the correct tests with respective observations.
(A) $\mathrm{CuSO}_4$ (acidified with acetic acid) $+\mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \rightarrow$ Chocolate brown precipitate.
(B) $\mathrm{FeCl}_3+\mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \rightarrow$ Prussian blue precipitate.
(C) $\mathrm{ZnCl}_2+\mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]$, neutralised with $\mathrm{NH}_4 \mathrm{OH} \rightarrow$ White or bluish white precipitate.
(D) $\mathrm{MgCl}_2+\mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \rightarrow$ Blue precipitate.
(E) $\mathrm{BaCl}_2+\mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]$, neutralised with $\mathrm{NaOH} \rightarrow$ White precipitate.
Choose the correct answer from the options given below :
Explanation
$2 \mathrm{CuSO}_4+\mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \xrightarrow{\mathrm{CH}_3 \mathrm{COOH}}\begin{aligned} &\mathrm{Cu}_2\left[\mathrm{Fe}(\mathrm{CN})_6\right]+2 \mathrm{~K}_2 \mathrm{SO}_4\\ &\text { (Chocolate brown ppt.) } \end{aligned}$
$4 \mathrm{FeCl}_3+3 \mathrm{~K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \longrightarrow \begin{aligned} &\mathrm{Fe}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]_3+12 \mathrm{KCl}\\ &\text { (Prussian Blue ppt.) } \end{aligned}$
$3 \mathrm{ZnCl}_4+2 \mathrm{~K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \xrightarrow{\mathrm{NH}_4 \mathrm{OH}}\underset{\text { (White or bluish white ppt.) }}{\mathrm{K}_2 \mathrm{Zn}_3\left[\mathrm{Fe}(\mathrm{CN})_6\right]_2+6 \mathrm{KCl}}$
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