A \( 20.0 \mathrm{~mL} \) solution containing \( 0.2 \mathrm{~g} \) impure \( \mathrm{H}_{2} \mathrm{O}_{2} \) reacts co…

A \( 20.0 \mathrm{~mL} \) solution containing \( 0.2 \mathrm{~g} \) impure \( \mathrm{H}_{2} \mathrm{O}_{2} \) reacts completely with \( 0.316 \mathrm{~g} \) of \( \mathrm{KMnO}_{4} \) in acid solution. The purity of \( \mathrm{H}_{2} \mathrm{O}_{2} \) (in %) is ...........
(mol. wt. of \( \mathrm{H}_{2} \mathrm{O}_{2}=34 \); mol. wt. of \( \mathrm{KMnO}_{4}=158 \) )