Chemistry - Complete d-block Question with Solution | TestHub

The catalytic activity of transition metals and their compounds is ascribed mainly to their ability of adopt variable oxidation states for example
$2\mathrm{S}{\mathrm{O}}_2+{\mathrm{O}}_2\stackrel{{\mathrm{V}}_2{\mathrm{O}}_5}{\to }2\mathrm{S}{\mathrm{O}}_3$
$\mathrm{S}{\mathrm{O}}_2+\stackrel{+5}{{\mathrm{V}}_2{\mathrm{O}}_5}\to \mathrm{S}{\mathrm{O}}_3+\stackrel{+4}{{\mathrm{V}}_2{\mathrm{O}}_4}$
$\stackrel{+4}{{\mathrm{V}}_2{\mathrm{O}}_4}+{\mathrm{O}}_2\to \stackrel{+5}{{\mathrm{V}}_2{\mathrm{O}}_5}$