Q.
An important oxidation-reduction reaction used to determine very small amounts of $O _{3}$ and other oxidants in polluted air involves oxidation of iodide ion :
$2 I ^{-}+ O _{3}+ H _{2} O \longrightarrow 2 OH ^{-}+ I _{2}+ O _{2}$
The solution is acidified and the $I _{2}$ is titrated with sodium thiosulphate solution using starch indicator. One litre of a mixture of $O _{3}$ and $O _{2}$ at STP was allowed to react with an excess of acidified solution of $KI$ and $I _{2}$ liberated required $40\, mL$ of $M / 10$ sodium thiosulphate solution. What is the mole or volume percentage of ozone in the mixture?
Redox Reactions
Solution: