Question

The magnetic moment of a certain complex (A) of Co was found to be 4.89 B.M. and the EAN as 36. Co also forms complex (B) with magnetic moment 3.87 B.M. and EAN 37, and complex (C) with EAN as 36 but diamagnetic. Which of the following statements is true regarding the above observation ?

• A. The oxidation states of Co in (A), (B), and (C) are +3, +2, and +3, respectively.
• B. Complexes (A) and (B) have $s{p}^3{d}^2$ hybridization state while (C) has $ds{p}^3$ hybridization state.
• C. The spin multiplicities of Co in (A), (B), and (C) are 4, 3, and 1, respectively.
• D. The oxidation states of Co in (A), (B), and (C) are +6, +8, and +1, respectively.

Answer 1

Answer: (A)

The oxidation states of Co in (A), (B), and (C) are +3, +2, and +3, respectively.

A- Magnetic moment- 4.89 BM. Hence the no. of unpaired electrons are 4.
$C{o}^{3+}-\left[Ar\right]3d^6$
Hybridization- $s{p}^3{d}^2$

B- Magnetic moment- 3.87 BM. Hence the no. of unpaired electrons are 3
$C{o}^{2+}-\left[Ar\right]3d^7$
Hybridization- $s{p}^3{d}^2$

C- Magnetic moment- 0 BM. Hence there is no unpaired electron..
$C{o}^{3+}-\left[Ar\right]3d^6$ (In presence of a strong field ligand)
Hybridization- $d^{2}s{p}^3$