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The strength of \( \mathrm{H}_{2} \mathrm{O}_{2} \) is expressed in several ways like molarity, normality,
\( \mathrm{P} \) \( \%(w / V) \), volume strength, etc. The strength of "10 V" means 1 volume of \( \mathrm{H}_{2} \mathrm{O}_{2} \) on decomposition gives 10 volumes of oxygen at \( 1 \mathrm{~atm} \) and \( 273 \mathrm{~K} \) or 1
W. litre of \( \mathrm{H}_{2} \mathrm{O}_{2} \) gives 10 litre of \( \mathrm{O}_{2} \) at \( 1 \mathrm{~atm} \) and \( 273 \mathrm{~K} \) The decomposition of \( \mathrm{H}_{2} \mathrm{O}_{2} \) is shown as under :
\[
\mathrm{H}_{2} \mathrm{O}_{2}(a q) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l)+\frac{1}{2} \mathrm{O}_{2}(g)
\]
\( \mathrm{H}_{2} \mathrm{O}_{2} \) can acts as oxidising as well as reducing agent. As oxidizing agent \( \mathrm{H}_{2} \mathrm{O}_{2} \) is converted into \( \mathrm{H}_{2} \mathrm{O} \) and as reducing agent \( \mathrm{H}_{2} \mathrm{O}_{2} \) is converted into \( \mathrm{O}_{2} \). For both cases its \( n \)-factor is 2 .
\( \therefore \) Normality of \( \mathrm{H}_{2} \mathrm{O}_{2} \) solution \( =2 \times \) Molarity of \( \mathrm{H}_{2} \mathrm{O}_{2} \) solution \( 40 \mathrm{~g} \mathrm{Ba}\left(\mathrm{MnO}_{4}\right)_{2} \) (mol. mass \( \left.=375\right) \) sample containing some inert impurities in acidic medium completely reacts with \( 125 \mathrm{~mL} \) of " \( 33.6 \mathrm{~V} \) " of \( \mathrm{H}_{2} \mathrm{O}_{2} \). What is the percentage purity of the sample?
(a) \( 28.12 \% \)
(b) \( 70.31 \% \)
(c) \( 85 \% \)
(d) None of these
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