If the density of a mixture of nitrogen and oxygen gases at $400 \ K$ and $1 \ atm$ pressure is $0.920 \ g \ L^{-1}$, what is the mole fraction of nitrogen in the mixture? ($R=0.082 \ L \ atm \ mol^{-1} \ K^{-1}$; assume ideal gas behavior for oxygen and nitrogen)

Two balloons $A$ and $B$ containing $0.2 \ mol$ and $0.1 \ mol$ of helium at room temperature and $2.0 \ atm$,respectively,are connected. When equilibrium is established,the final pressure of $He$ in the system is $.... \ atm$.

What is the relationship between viscosity and density?

If the distance between two gas molecules becomes half,what change occurs in the London dispersion forces?

Two flasks $I$ and $II$ shown below are connected by a valve of negligible volume. When the valve is opened,the final pressure of the system in bar is $x \times 10^{-2}$. The value of $x$ is $.....$ . (Integer answer) [Assume-Ideal gas; $1 \, bar = 10^{5} \, Pa$; Molar mass of $N_{2} = 28.0 \, g \, mol^{-1}$; $R = 8.31 \, J \, mol^{-1} \, K^{-1}$]

At $27^{\circ} C$, $500 \ mL$ of helium diffuses in $30 \ minutes$. What is the time (in hours) taken for $1000 \ mL$ of $SO_2$ to diffuse under the same experimental conditions?