JEE MAIN - Chemistry (2022 - 25th June Evening Shift - No. 20)
Amongst FeCl3.3H2O, K3[Fe(CN)6] and [Co(NH3)6]Cl3, the spin-only magnetic moment value of the inner-orbital complex that absorbs light at shortest wavelength is ____________ B.M. [nearest integer]
Answer
2
Explanation
$\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3} \mathrm{Cl}_{3}\right] \rightarrow$ Outer-orbital complex
$$ \mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right] \rightarrow \text { Inner-orbital complex } $$
$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3} \rightarrow$ Inner-orbital complex
Since $\mathrm{CN}^{-}$is a strong field ligand than $\mathrm{NH}_{3}$. Hence $\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]$ is the inner-orbital complex that absorbs light at shortest wavelength.
$\mathrm{Fe}(\text{III}) \rightarrow$ valence shell configuration $3 \mathrm{~d}^{5}$
Since $\mathrm{CN}^{-}$will do pairing, so unpaired electron $=1$
$$ \mu=\sqrt{1(1+2)}=\sqrt{3} \mathrm{BM} \simeq 2 \mathrm{BM} $$
$$ \mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right] \rightarrow \text { Inner-orbital complex } $$
$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3} \rightarrow$ Inner-orbital complex
Since $\mathrm{CN}^{-}$is a strong field ligand than $\mathrm{NH}_{3}$. Hence $\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]$ is the inner-orbital complex that absorbs light at shortest wavelength.
$\mathrm{Fe}(\text{III}) \rightarrow$ valence shell configuration $3 \mathrm{~d}^{5}$
Since $\mathrm{CN}^{-}$will do pairing, so unpaired electron $=1$
$$ \mu=\sqrt{1(1+2)}=\sqrt{3} \mathrm{BM} \simeq 2 \mathrm{BM} $$
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