Question

$2$ moles of a mixture of $O_2$ and $O_3$ is reacted with excess of acidified solution of $KI$. The iodine liberated require $1L$ of $2M$ hypo solution for complete reaction. The weight $\%$ of $O_3$ in the initial sample is $x$.

The value of $\frac{x}{10}$ is :

• A. $8$
• B. $4$
• C. $2$
• D. $6$

Answer 1

The correct option is D $6$

$2$ moles of a mixture of $O_2$ and $O_3$ is reacted with excess of $KI.$

The reactions areas follows:
$\underset{\underset{moles=x}{v.f=2}}{KI+O_3}\to \underset{v.f=2}{I_2+H_{2}O+O_2}$
$\underset{v.f=2}{I_2}+\underset{\underset{\underset{v.f=1}{V=1L}}{M=2}}{N{a}_2{S}_2{O}_3}\to I^{-}+N{a}_2{S}_4{O}_6$
Eq. of $O_3=$ Eq. of $I_2=$ Eq. of hypo
Equivalent = Moles x valency factor
$\Rightarrow 2\times x=2\times 1$
$x=1$ mole
$\Rightarrow Weightof{O}_3=\frac{1\times 48}{1\times 48+1\times 32}\times 100$
$=\frac{3}{5}\times 100=60\%$

$\frac{x}{10}=\frac{60}{10}=6$