Question

$[P d (F )(C l)(B r)(I)]^{2-}$ has n number of geometrical isomers. Then, the spin-only magnetic moment and crystal field stabilisation energy [CFSE] of $[Fe(CN)_6]^{n -6}$, respectively, are:
[Note : Ignore the pairing energy]

• A. 1.73 BM and -2.0 $\Delta_{0}$
• B. 2.84 BM and -1.6 $\Delta_{0}$
• C. 0 BM and - 2.4 $\Delta_{0}$
• D. 5.92 BM and 0

Answer 1

Answer: (A)

$\left[Pb\left(F\right)\left(CI\right)\left(Br\right)\left(I\right)\right]^{2-}$ have three geometrical isomer so formula for $\quad\left[Fe\left(CN\right)_{6}\right]^{n-6} \, is\, \left[Fe\left(CN\right)_{6}\right]^{3-}$ and CFSE for this complex is
$\quad Fe^{3\oplus} \Rightarrow \, 3d^{5} 4S^{\circ}$
Magnetic Moment =$\sqrt{3}=1.73 B.M$
$CFSE=\left[\left(-0.4\times5\right)+\left(0.6\times0\right)\right]\Delta_{0}=-2.0 \Delta_{0}$