One litre of a mixture of `O_(2) " and " O_(3)` at NTP was allowed to react with an excess of acidified solution of KI. The iodine liberated required 40 mL of `M//10` sodium thiosulphate solution for titration. What is the weight per cent of ozone in the decompose ozone. Assuming that one photon can decompose one ozone molecule, how many photon can decompose required for the complete decomposition of ozone in the original mixture ?

Explanation

Let the total moles of `O_(2) " and" O_(3)` in the mixture be n.
Applying PV=nRT
`1xx1=nxx0.0821xx273`
n=0.044 mole
Moles of `O_(3)`= moles of `I_(2)=1//2` moles of `Na_(2)S_(2)O_(3)`
`=(1)/(2)xx(1)/(10)xx(40)/(1000)=0.002` moles
Moles of `O_(2)` in the mixture `=0.044-0.002=0.042` moles
Mass of `O_(2)=0.042xx32=1.344 g`
Mass of `O_(3)=0.002xx48=0.096 g`
`% O_(3)=(0.096)/(1.44)xx100=6.67`
No of photons required to decompose 0.002 moles of ozone
`=0.002xx6.02xx10^(23)`
`=1.204xx10^(21)`