Explanation

(b) Neglecting bond length, the volume of an oxygen molecule has been taken as 2 times that of one oxygen atom.
In $22.4\ litres\ i.e.,\ 22.4 \times 10^{- 3}m^{3},$ there are
$N_{A} = 6.23 \times 10^{23}$ molecules
Total volume of oxygen molecules $= 2 \times \frac{4}{3}\pi r^{3} \times N_{A}$
$22.4 \times 10^{- 3}m^{3}$ is occupied by $N_{A}$ molecules
$\therefore$ Fraction of volume occupied
$= \frac{2 \times \frac{4}{3} \times \pi \times \left( 1.5 \times 10^{- 10} \right)^{3} \times 6.2 \times 10^{23}}{(22.4 \times 10^{- 3})} = 8 \times 10^{- 4}$