Seema Saini Solutions for Chapter: States of Matter, Exercise 6: DPP 4.6

The critical temperature of ${\mathrm{O}}_2$ is less than ${\mathrm{H}}_2\mathrm{O}$ because the ${\mathrm{H}}_2\mathrm{O}$ molecules have:

It is easier to liquify ${\mathrm{O}}_2$ than ${\mathrm{H}}_2$ because: 

The mean free path $\left(\mathrm{\lambda }\right)$ of a gas sample is given by (Symbols have usual meaning):

The ratio of Boyle's temperature and critical temperature of a gas is:

The gases showing heating and cooling effects during the Joule Thomson's experiment will have Joule-Thomson coefficient :

Compressibility factor $\left(\mathrm{Z}=\frac{\mathrm{PV}}{\mathrm{nRT}}\right)$ is plotted against pressure:

What is the correct order of liquefiability of the gases shown in the above graph? 

Which of the following facts regarding the mean free path of gaseous molecules is/are correct?

Which of the following statements is not correct?