On what factor does the magnitude of surface tension depend?

At a certain temperature and pressure,helium diffuses $n$ times faster than methane. Find the value of $n$.

The rate of effusion of a gas is directly proportional to.....

The rate of diffusion of $SO_2$,$CO_2$,$PCl_3$ and $SO_3$ are in the following order:

$360 \ cm^3$ of a hydrocarbon diffuses in $30$ minutes, while under the same conditions $360 \ cm^3$ of $SO_2$ gas diffuses in one hour. The molecular formula of the hydrocarbon is

Which of the following relations is true based on the partial pressure and mole fraction?