Question

Match List - I with List - II.

List - I		List - II
(a)	[Fe(CN)6]3−	(i)	5.92 BM
(b)	[Fe(H2O)6]3+	(ii)	0 BM
(c)	[Fe(CN)6]4−	(iii)	4.90 BM
(d)	[Fe(H2O)6]2+	(iv)	1.73 BM

Choose the correct answer from the options given below.

• A. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
• B. (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
• C. (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
• D. (a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)

Answer 1

The Correct Option is A

To correctly match the complexes given in List I with their respective magnetic moments in List II, we need to understand the electronic configuration of the central metal ion and the ligand field created by associated ligands. The magnetic moment (\( \mu \)) can be calculated using the formula:

\[\mu = \sqrt{n(n+2)}\]

where \( n \) is the number of unpaired electrons.

1. [Fe(CN)₆]³⁻: In this complex, iron is in the +3 oxidation state (\(Fe^{3+}\)), and the CN^- ligands create a strong field, causing a low-spin configuration with none of the electron's unpaired.
   Magnetic moment: \(0 \, \text{BM}\) (0 unpaired electrons matching option (ii)).
2. [Fe(H₂O)₆]³⁺: Here, iron is also in the +3 oxidation state (\( Fe^{3+} \)), but water, acting as a weak field ligand, causes a high-spin configuration with 5 unpaired electrons.
   Magnetic moment: \(\sqrt{35} = 5.92 \, \text{BM}\) (5 unpaired electrons matching option (i)).
3. [Fe(CN)₆]⁴⁻: For this complex, iron is in the +2 oxidation state (\(Fe^{2+}\)), and again CN^- is a strong field ligand resulting in a low-spin configuration with no unpaired electrons.
   Magnetic moment: \(0 \, \text{BM}\) (0 unpaired electrons matching option (ii)).
4. [Fe(H₂O)₆]²⁺: In this scenario, iron is in the +2 oxidation state (\(Fe^{2+}\)), and with water as a weak field ligand, it is a high-spin complex with 4 unpaired electrons.
   Magnetic moment: \(\sqrt{24} = 4.90 \, \text{BM}\) (4 unpaired electrons matching option (iii)).

Based on the above analysis, the correct matches are:

• (a) [Fe(CN)₆]³⁻ - (ii) 0 BM
• (b) [Fe(H₂O)₆]³⁺ - (i) 5.92 BM
• (c) [Fe(CN)₆]⁴⁻ - (ii) 0 BM
• (d) [Fe(H₂O)₆]²⁺ - (iii) 4.90 BM

Therefore, the correct answer is: (a)-(ii), (b)-(i), (c)-(ii), (d)-(iii).