What is the effect of a decrease in the number of molecules per unit volume on the mean free path?

Estimate the mean free path for a water molecule in water vapour at $373 \; K$. The density of water is $1000 \; kg \; m^{-3}$. The density of water vapour at $100 \; ^{\circ}C$ and $1 \; atm$ pressure is $0.6 \; kg \; m^{-3}$. The volume of a molecule multiplied by the total number gives,what is called,molecular volume.

The value of $C_p - C_v = 1.00 R$ for a gas in state $A$ and $C_p - C_v = 1.06 R$ in another state $B$. If $P_A$ and $P_B$ denote the pressure and $T_A$ and $T_B$ denote the temperature in the two states,then:

$A$ system consists of two types of gas molecules $A$ and $B$ having the same number density $2 \times 10^{25} \, /m^3$. The diameters of $A$ and $B$ are $10 \, \mathring{A}$ and $5 \, \mathring{A}$ respectively. They undergo collisions at room temperature. The ratio of the average distance covered by molecule $A$ to that of $B$ between two successive collisions is $..... \times 10^{-2}$.

The internal energy of real gases is determined by which of the following?

For the given concentration,if the ratio of the diameters of the molecules of two gases is $1: 2$,then the ratio of their mean free paths is