The ratio of the rate of diffusion of $SO_2$ to $CH_4$ is

The rate of diffusion of a gas is

$50 \ mL$ of hydrogen diffuses out through a small hole from a vessel in $20 \ min$. The time needed for $40 \ mL$ of oxygen to diffuse out is ............. $min$.

The rate of diffusion of $SO_{2}$,$CO_{2}$,$PCl_{3}$ and $SO_{3}$ are in the following order:

Normal boiling point of water is $373 \ K$ (at $760 \ mm$). Vapour pressure of water at $298 \ K$ is $23 \ mm$. If the enthalpy of evaporation is $40.656 \ kJ/mole$,the boiling point of water at $23 \ mm$ pressure will be ............. $K$.

$A$ sample of air contains $N_2$ and $O_2$ saturated with water vapor,with a total pressure of $640 \ torr$. If the water vapor pressure is $40 \ torr$ and the molar ratio of $N_2$ to $O_2$ is $3 : 1$,what is the partial pressure of $N_2$ in the sample in $torr$?