Question

Among $C{o}^{3+},T{i}^{2+},V^{2+}\text{and}C{r}^{2+}$ ions, one if used as
a reagent cannot liberate $H_2$ from dilute mineral acid solution, its spin-only magnetic moment in gaseous state is B.M. (Nearest integer)

• A. 5.0
• B. 5.00
• C. 5

Answer 1

Answer: (A), (B), (C)

$C{o}^{3+}$ will not liberate $H_2$ gas an reaction with dilute
acid
$E_{C{o}^{3+}/C{o}^{2+}}^{\circ }=+1.97$
And $C{o}^{3+}$ has electronic configuration $=\left[Ar\right]3d^6$
$\therefore 4\text{unpaired}{e}^{–}$ are present in it
$\therefore$ Spin-only magnetic moment $=\sqrt{4(4+2)}$
$=4.92$
$\approx 5$