The rate of diffusion of a gas is inversely proportional to

Explain the vapour pressure of a liquid.

In a mixture of $CO_2$ and $CH_4$ in a closed vessel at a constant temperature,the total pressure is $8.3 \times 10^4 \, Pa$. If the partial pressure of $CO_2$ is $2.8 \times 10^4 \, Pa$,what will be the partial pressure of $CH_4$?

If some moles of $O_2$ diffuse in $18 \ sec$ and the same moles of another gas diffuse in $45 \ sec$,what is the molecular weight of the unknown gas?

The rate of diffusion of a gas is proportional to

Fill in the blanks:
$(1)$ The properties of gases were first measured by ......... .
$(2)$ The dipole-dipole interaction energy between stationary polar molecules is proportional to .......... .
$(3)$ The interaction energy between rotating polar molecules is proportional to .......... .
$(4)$ The bond energy of a hydrogen bond is about ......... $kJ \ mol^{-1}$.