A solution of $\mathrm{FeCl}_{3}$ when treated with $\mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]$ gives a prussiun blue precipitate due to the formation of

(D) $\mathrm{Fe}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]_{3}$

(A) $\mathrm{K}\left[\mathrm{Fe}_{2}(\mathrm{CN})_{6}\right]$

(B) $\mathrm{Fe}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]$

(C) $\mathrm{Fe}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]_{2}$

JEE Main · 2023 · 01 Feb 2023 · Shift 1 · Coordination Compounds

A solution of

FeCl_{3}

when treated with

K_{4} [Fe (CN)_{6}]

gives a prussiun blue precipitate due to the formation of

(A) $K [Fe_{2} (CN)_{6}]$
(B) $Fe [Fe (CN)_{6}]$
(C) $Fe_{3} [Fe (CN)_{6}]_{2}$
(D) $Fe_{4} [Fe (CN)_{6}]_{3}$ ✓ Correct

Answer: (D)

Solution

Prussian blue forms when iron(III) from ferric chloride meets the hexacyanidoferrate(II) ion supplied by potassium ferrocyanide. The

F e^{3 +}

cations and the

[Fe (CN)_{6}]^{4 -}

anions combine in the ratio that balances their charges, four trivalent cations to three tetravalent anions, giving ferric ferrocyanide

F e_{4} [Fe (CN)_{6}]_{3}

. This is the deep blue precipitate observed.

JEE Main · 2023 · 01 Feb 2023 · Shift 1 · Single correct option

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