PX154 - C8 - collisions between molecules

near the end of [YF 18.3]

t_{m e a n} = \frac{1}{4 π \sqrt{2}} \frac{V}{r^{2} v_{r m s} N}

$r =$ radius of a spherical molecule

$N_{2} a t S T P : t_{m e a n} = 1.2 \times 10^{- 10} s$
then mean distance travelled between collisions can be defined as "the mean free path", $λ$ :

λ = v_{r m s} t_{m e a n} = \frac{V}{4 π \sqrt{2} r^{2} N}

λ = \frac{k_{B} T}{4 π \sqrt{2} r^{2} p}

$N_{2} a t S T P : t_{m e a n} = 1.2 \times 10^{- 10} s, λ = 5.8 \times 10^{- 8} m (\approx 300 r_{N_{2}})$