5.0 cm³ of H₂O₂ liberates 0.508 g of iodine from an acidified KI solution. The strength of H₂O₂ solution in terms of volume strength at STP is

$$\begin{gathered} {\mathrm{V}}_{{\mathrm{H}}_2{\mathrm{O}}_2}=5 \mathrm{ml} \\ {\mathrm{W}}_{{\mathrm{I}}_2} =0.508\mathrm{gr} \\ {\mathrm{MW}}_{{\mathrm{I}}_2}=2\times 127=254\mathrm{gr} \\ {\mathrm{H}}_2{\mathrm{O}}_2+2\mathrm{KI}\stackrel{{\mathrm{H}}^{+}}{\to }{\mathrm{I}}_2+2\mathrm{KOH} \\ 1\mathrm{mole}----1 \mathrm{mole} \\ ?? ----- 2\times {10}^{-3} \mathrm{mole} \\ \frac{2\times {10}^{-3}\times 1}{1} \\ \mathrm{M}=2\times {10}^{-3}\times \frac{1000}{5} \\ \mathrm{M}=0.4\mathrm{M} \end{gathered}$$

For H₂O₂

10 vol. strength =0.893M = 1.786N = 3.03%(W/V)
?? -------------------------= 0.4M
 $\frac{0.4\times 10}{0.893} =\frac{4}{0.893}=4.47 \mathrm{vol}$