How does the mean free path vary with the number density of a gas?

An experiment is carried out on a fixed amount of gas at different temperatures and at high pressure such that it deviates from ideal gas behavior. The variation of $\frac{PV}{RT}$ with $P$ is shown in the diagram. The correct variation will correspond to

The mean free path of a molecule of $He$ gas is $\alpha$. Its mean free path along any arbitrary coordinate axis will be ...........

We have $0.5 \, g$ of hydrogen gas in a cubic chamber of size $3 \, cm$ kept at $NTP$. The gas in the chamber is compressed keeping the temperature constant until a final pressure of $100 \, atm$ is reached. Is one justified in assuming the ideal gas law in the final state? (Hydrogen molecules can be considered as spheres of radius $1 \, \mathring{A}$).

For a molecule of an ideal gas,the number density is $2 \sqrt{2} \times 10^8 \text{ cm}^{-3}$ and the mean free path is $\frac{10^{-2}}{\pi} \text{ cm}$. The diameter of the gas molecule is

The mean free path of a molecule of diameter $5\times10^{-10} \ m$ at the temperature $41^{\circ}C$ and pressure $1.38\times10^{5} \ Pa$ is given as . . . . . . $m$. (Given $k_{B}=1.38\times10^{-23} \ J/K$).