What are the measurable properties of a gas?

Under identical conditions,the time required for the diffusion of $64 \ mL$ of $H_2$ gas is equal to the time required for the diffusion of which of the following?

Show the relationship between different units of pressure.

If equal masses of $CO$ and $N_2$ are filled in a container,the relationship between their partial pressures will be ................

At a constant temperature and pressure,the ratio of the densities of two gases is $1 : 16$. The ratio of their rates of diffusion will be ........

If $N_2, O_2, H_2$,and $He$ gases are filled separately in four car tubes at the same pressure,which gas will diffuse first?