The mass of ${\mathrm{H}}_2{\mathrm{O}}_2$ that is completely oxidised by 30.2 g of  ${\mathrm{KMnO}}_4$ (molar mass= $=158\mathrm{g}{\mathrm{mol}}^{-1}$) in acidic medium is

The reaction is $2{\mathrm{KMnO}}_4+5{\mathrm{H}}_2{\mathrm{O}}_2+6{\mathrm{H}}^{+}⟶2{\mathrm{Mn}}^{2+}+5{\mathrm{O}}_2+8{\mathrm{H}}_2\mathrm{O}+2{\mathrm{K}}^{+}$

$2\times 151\mathrm{g}$ of  ${\mathrm{KMnO}}_4$ reacts completely with $5\times 34g$ of  ${\mathrm{H}}_2{\mathrm{O}}_2$

$30.2\mathrm{g}$ of  ${\mathrm{KMnO}}_4$ reacts completely with  $\frac{5\times 34{\mathrm{gH}}_2{\mathrm{O}}_2}{2\times 151\mathrm{g}{\mathrm{KMnO}}_4}\left(30.2\mathrm{g}{\mathrm{KMnO}}_4\right)=17{\mathrm{gH}}_2{\mathrm{O}}_2$