QJEEM22Che739: JEE Main 2022 Chemistry - Class 12 JEEM22Che739 Solution: Spin only magnetic moment ( s ) of is ____________ B.M.…

$\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]$

$\mathrm{CN}^{-}$ have $-1$ oxidation State.

Let oxidation state of $\mathrm{Fe}$ in the complex is $x$ .

So, $x-6=-3 \Rightarrow x=+3$

Now, $\mathrm{CN}^{-}$ ion is a strong field ligand.

For $Fe^{3+}: -3d^54s^0$

Unpaired electron $=1$

$\mu_{\mathrm{B}}=\sqrt{n(n+2)}=\sqrt{1 \times(1+2)}=1.7$

$\mu_{\mathrm{B}}=2$ B.M