Ozone an estimated in air by passing certaing volume of air through an acidified or neutral or basic KI solution when `O_(2)` is evolved and `I^(ɵ)` is oxidised to `I_(2)`. Free `I_(2)` evolved is titrated with standard `Na_(2)S_(2)O_(3)` solution. In an experiment 10 L of air at 1 atom and `27^@C` was passed through an alkaline KI solution and `I_(2)` liberated requried 2 " mL of " `(M)/(800)Na_(2)S_(2)O_(3)` solution. Calculate the volume percentage of `O_(3)` in sample.

Explanation

Write the balanced redox reactions in basic medium.
`2I^(ɵ)+H_(2)O+O_(3)toO_(2)+I_(2)+2overset(ɵ)(O)H` (n factor `O_(3)=2`)
`I_(2)+2e^(-)to2I^(ɵ)(n=2)`
`S_(2)O_(3)+10overset(ɵ)(O)Hto2SO_(4)^(2-)+5H_(2)O+8e^(-)(n=8)`
`thereforem" Eq of "I_(2)=m" Eq of "Na_(2)S_(2)O_(3)`
`=2xx(1)/(800)xx8` (n factor)
`=0.02`
mmol es of `I_(2)=(0.02)/(2)=mmol es of O_(3)`
`[becausen=2` for both or molar ratio of `O_(3):I_(2)::1:1`]
`P_(O_(3))=(nRT)/(V)`
`=(0.01xx10^(-3)xx0.0821xx300)/(10)`
`=246.3xx10^(-7)atm`
Volume `% of O_(3)=246.3xx10^(-7)xx100`
`=2.463xx10^(-3)%`