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Question: Answered & Verified by Expert
Which one of the following gives Prussian blue colour?
ChemistryCoordination CompoundsTS EAMCETTS EAMCET 2013
Options:
  • A $\mathrm{Fe}_2\left[\mathrm{Fe}(\mathrm{CN})_6\right]$
  • B $\mathrm{Na}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]$
  • C $\mathrm{Fe}_3\left[\mathrm{Fe}(\mathrm{CN})_6\right]_3$
  • D $\mathrm{Fe}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]_3$
Solution:
2532 Upvotes Verified Answer
The correct answer is: $\mathrm{Fe}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]_3$
Ferric salts (such as $\mathrm{FeCl}_3$ ) form Prussian blue (blue ppt or colouration) with potassium ferrocyanide.
$$
\begin{array}{r}
4 \mathrm{FeCl}_3+3 \mathrm{~K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \longrightarrow \underset{\substack{\text { Prussian blue } \\
\text { (ferric ferrocyanide) }}}{\mathrm{Fe}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]_3} \\
+12 \mathrm{KCl}
\end{array}
$$

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