Gas $X$ diffuses three times faster than gas $Y$. What is the ratio of their densities,i.e.,$D_x : D_y$?

What is the coefficient of viscosity? Give its unit.

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

If $H_2S$ and $NH_3$ gases are released simultaneously from a cylinder through a small hole,which gas will be detected first and why?

The $\%$ composition by volume of $Cl_2, H_2$,and $N_2$ are in $1:2:7$ by proportion. If the total pressure is $40 \ bar$,find the partial pressures of each gas?
[ Partial pressure $= \frac{\text{Volume } \% \times \text{Total pressure}}{100} ]$

Which of the following mixtures of gases does not obey Dalton's law of partial pressure?