Question

A complex [CoL₆]ⁿ⁺ where L is neutral ligand has a magnetic moment m = 4.5 B. M. Hence,
(a) Co must be in +2 oxidation state
(b) L must be a strong ligand
(c) Co must be in +3 oxidation state
(d) None of these

Answer 1

${\huge {\mathfrak {Answer :-}}}$

➡️ Option (B)

That's it..

Answer 2

Solution : A complex [CoL₆]ⁿ⁺ where L is neutral ligand has a magnetic moment m = 4.5 B. M. Hence, Co must be in +3 oxidation state

• The formula of magnetic moment is $\sqrt{n(n+2)}$ where n is the number of unpaired electrons. Magnetic moment 4.5 means n is 4 so number of unpaired electrons is 4
• Now since L is a neutral ligand therefore the charge n+ will go to cobalt i.e. $Co^{+n}$
• Now electrotonic configuration of Co is [Ar] $3d^{7}4s^{2}$
• If the oxidation state of Co is +2 it means that Co loose 2 electrons so electronic configuration of Co in +2 oxidation state will be [Ar] $3d^{7}$and the by the energy level diagram given on the picture it is clear that it will have 3 unpaired electrons which is not possible
• When the Co is in +3 oxidation state it means it will loose 3 electrons so its electronic configuration will be [Ar] $3d^{6}$ and by the energy level diagram given on the picture it is clear that it will have 4 unpaired electrons.
• So option c is correct

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