Modern vacuum pumps can evacuate a vessel downto a pressure of 4.0 × 10^-15 atm. at room temperature (300 K). Taking R =8.3 JK^-1 mole^-1, 1 atm…

Modern vacuum pumps can evacuate a vessel downto a pressure of $\displaystyle 4.0 \times 10^{-15} \mathrm{~atm}$. at room temperature ($\displaystyle 300$ K). Taking $\displaystyle \mathrm{R}=8.3 \mathrm{JK}^{-1} \mathrm{~mole}^{-1}, 1 \mathrm{~atm}=10^5 \mathrm{~Pa}$ and $\displaystyle \mathrm{N}_{\text {Avogadro }}=6 \times 10^{23}$ mole $\displaystyle ^{-1}$, the mean distance between molecules of gas in an evacuated vessel will be of the order of :