On what factor does the magnitude of surface tension depend?

The ratio of the rate of diffusion of a given element to that of helium is $1.4$. The molecular weight of the element is

Mountaineers carry oxygen cylinders with them because ...

State Dalton$'$s law of partial pressures.

$A$ 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 $torr$?

$50 \ mL$ of hydrogen gas diffuses through a small hole in a container in $20 \ min$. How much time (in $min$) will $40 \ mL$ of oxygen take to diffuse under the same conditions?