Question

Among Co3+, Ti2+, V2+ and Cr2+ ions, one if used as a reagent cannot liberate H2 from dilute mineral acid solution, its spin-only magnetic moment in gaseous state is________ B.M. (Nearest integer)

Answer 1

Co3+ will not liberate H2 gas in reaction with dilute acid
$\frac{EºCo^{3+}}{Co^{2+}}$=+1.97
And Co3+ has electronic configuration = [Ar] 3 d 6
∴ four unpaired electrons are present in it.
∴ spin only magnetic moment=$\sqrt{4(4+2)}$=4.92≈5