Question

A $5.0 \,cm^3$ solution of $H_2O_2$ liberates $0.508\, g$ of iodine from an acidified $KI$ solution. Calculate the strength of $H_2O_2$ solution in terms of volume strength at STP.

Answer 1

The redox reaction involved is
$ H_2O_2 +2I^- +2H^+ \rightarrow 2H_2 O +I_2$
If $M$ is molarity of $H_2 O_2$ solution, then
$ 5M =\frac{0.508 \times 1000}{254}(\because 1 $ mole $ H_2O_2 \equiv \, 1 $ mole $I_2)$
$\Rightarrow M=0.4$
Also, $n$-factor of $H_2O_2$, is $2$, therefore normality of $H_2O_2$ , solution is $0.8\, N$.
$\Rightarrow \, \, $ Volume strength = Normality $\times 5.6 = 0.8 \times 5.6 = 4.48\, V$