JEE Main · 2022 · 27 Jul 2022 · Shift 2 · Coordination Compounds

WhatsApp Email

Fe^{3 +}

cation gives a prussian blue precipitate on addition of potassium ferrocyanide solution due to the formation of:

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

Answer: (D)

Solution

When Fe³⁺ reacts with potassium ferrocyanide [K₄Fe(CN)₆], it forms Prussian blue, which has the formula Fe₄[Fe(CN)₆]₃. The reaction is:

4 Fe^{3 +} + 3 [Fe (CN)_{6}]^{4 -} \to Fe_{4} [Fe (CN)_{6}]_{3}

This deep blue precipitate is known as Prussian blue or ferric ferrocyanide, and is a classic qualitative test for Fe³⁺ ions.

JEE Main · 2022 · 27 Jul 2022 · Shift 2 · Single correct option

Practise more: all JEE Main PYQs on Coordination Compounds →

More JEE Main questions on Coordination Compounds

Given below are two statements:

Statement I: Among $[Cu (NH_{3})_{4}]^{2 +}$ , $[Ni (en)_{3}]^{2 +}$ , $[Ni (NH_{3})_{6}]^{2 +}$ and $[Mn (H_{2} O)_{6}]^{2 +}$ , …
JEE Main 2026View solution →
Consider the transition metal ions $Mn^{3 +}, Cr^{3 +}, Fe^{3 +}$ and $Co^{3 +}$ and all form low spin octahedral complexes. The correct decreasing order of unpaired electrons in their respective d-orbitals of the complexes is
JEE Main 2026View solution →
A first row transition metla (M) does not liberate $H_{2}$ gas from dilute HCl .1 mol of aqueous solution of $MSO_{4}$ is treated with excess of aqueous KCN and then $H_{2} S (g)$ is passed through the solution. The amount of MS …
JEE Main 2026View solution →
Given below are two statements:

Statement I: Crystal Field Stabilization Energy (CFSE) of $[Cr (H_{2} O)_{6}]^{2 +}$ is greater than that of $[Mn (H_{2} O)_{6}]^{2 +}$ .

Statement II: Pot …
JEE Main 2026View solution →
Identify the metal ions among $Co^{2 +}$ , $Ni^{2 +}$ , $Fe^{2 +}$ , $V^{3 +}$ and $Ti^{2 +}$ having a spin-only magnetic moment value more than 3.0 BM. The sum of unpaired electrons present in the high spin octahedral complexes formed by thos …
JEE Main 2026View solution →
$[Ni (PPh_{3})_{2} Cl_{2}]$ is a paramagnetic complex. Identify the INCORRECT statements about this complex.
A. The complex exhibits geometrical isomerism.
B. The complex is white in colour.
C. The calculated spin-only magnetic moment of the complex is 2. …
JEE Main 2026View solution →