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QJEEAdv15Ch7dc5: JEE Advanced 2015 Chemistry - Class 12 JEEAdv15Ch7dc5 Solution: For the octahedral complexes of Fe 3+ in SCN (thiocyana-to-S)…

For the octahedral complexes of Fe3+ in SCN −- (thiocyana-to-S) and in CN −- ligand environments, the difference between the spin-only magnetic moments in Bohr magnetons (when approximated to the nearest integer) is __________.

[Atomic number Fe = 26]

Step-by-Step Verified Solution

The spin only magnetic moment is given by μ=n(n+1)\mu = \sqrt {n(n + 1)} , where n is the number of unpaired electrons.

Fe3+ complex with weak field ligand SCN −- contains five unpaired electrons.

JEE Advanced 2015 Paper 1 Offline Chemistry - Coordination Compounds Question 27 English Explanation 1

Therefore, μ\mu = 5.9 BM.

Fe3+ complex with strong field ligand CN −- contains one unpaired electron.

JEE Advanced 2015 Paper 1 Offline Chemistry - Coordination Compounds Question 27 English Explanation 2

Therefore, μ\mu = 1.73 BM.

Thus, the difference in spin only magnetic moment is ≈\approx 4.

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