Question

The difference between spin only magnetic moment value of $[Co(H_2O)_6]Cl_2$ and $[Cr(H_2O)_6]Cl_3$ is ________ .

Answer 1

$Co → 4s^2 3d^7$
$H_2O$ is weak field ligand.
$CO^{2+}→3d^7$
$n=3$
$μ_1=\sqrt {n(n+2)}$
$μ_1=\sqrt {15}$ B.M.
$Cr →4s^1 3d^5$
$CO^{3+}→3d^3$
$n=3$
$μ_2=\sqrt {15}$ B.M.
$μ_1–μ_2=0$

So, the answer is $2$.