Question

Match the following List -I (Complex) List II (Spin only Magnetic Moment)

	List -I (Complex)		List II (Spin only Magnetic Moment)
A)	[CoF6]3-	I)	0
B)	[Co(C2O4)3]3-	II)	√24
C)	[FeF6]3+	III)	√8
D)	[Mn(CN)6]3-	IV)	√35
		V)	√15

the correct answer is:

• A. A-V, B - II, C - IV, D - I
• B. A - II, B - I, C- IV, D - III
• C. A - II, B - I, C - V, D - III
• D. A - III, B - II, C - I, D - V

Answer 1

The Correct Option is A

Step 1: Understand the Concept of Magnetic Moment:
The magnetic moment for a transition metal complex can be calculated using the formula for spin-only magnetic moment: $$\mu = \sqrt{n(n + 2)}$$ where \(n\) is the number of unpaired electrons in the complex. The spin-only magnetic moment is determined by the number of unpaired electrons, which depends on the metal's oxidation state and the nature of the ligands.

Step 2: Analyze Each Complex and Determine the Number of Unpaired Electrons:

• A) [CoF₆] ^3-: Cobalt in +3 oxidation state (Co³⁺) has 6 d-electrons (d⁶). In the octahedral complex with weak field ligands like fluoride (F^-), the electrons will be arranged with 3 unpaired electrons. Therefore, the number of unpaired electrons is 3.
• B) [Co(C₂O₄)₃] ^3-: Cobalt in +3 oxidation state (Co³⁺) has 6 d-electrons (d⁶). The oxalate ion (C₂O₄^2-) is a weak field ligand, so there are 2 unpaired electrons in this complex.
• C) [FeF₆] ^3-: Iron in +3 oxidation state (Fe³⁺) has 5 d-electrons (d⁵). With weak field fluoride ligands, Fe³⁺ has 5 unpaired electrons.
• D) [Mn(CN)₆] ^3-: Manganese in +3 oxidation state (Mn³⁺) has 4 d-electrons (d⁴). Cyanide (CN^-) is a strong field ligand, causing pairing of electrons, resulting in 1 unpaired electron.

Step 3: Calculate the Magnetic Moment:
- For complex A: With 3 unpaired electrons, the magnetic moment is: $$\mu = \sqrt{3(3 + 2)} = \sqrt{15}$$ - For complex B: With 2 unpaired electrons, the magnetic moment is: $$\mu = \sqrt{2(2 + 2)} = \sqrt{8}$$ - For complex C: With 5 unpaired electrons, the magnetic moment is: $$\mu = \sqrt{5(5 + 2)} = \sqrt{35}$$ - For complex D: With 1 unpaired electron, the magnetic moment is: $$\mu = \sqrt{1(1 + 2)} = \sqrt{3}$$

Step 4: Match the Complexes to Their Magnetic Moments:

• A) [CoF₆] ^3-: $\mu = \sqrt{15}$ (matches with V)
• B) [Co(C₂O₄)₃] ^3-: $\mu = \sqrt{8}$ (matches with III)
• C) [FeF₆] ^3-: $\mu = \sqrt{35}$ (matches with IV)
• D) [Mn(CN)₆] ^3-: $\mu = \sqrt{3}$ (matches with II)

Final Answer:
The correct matching is: A - V, B - II, C - IV, D - I