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 $.... \ atm$.

The correct value of the universal gas constant $R$ is:

What is the temperature at which the kinetic energy of $0.3 \text{ moles}$ of helium is equal to the kinetic energy of $0.4 \text{ moles}$ of argon at $400 \text{ K}$ (in $\text{ K}$)?

The density of a mixture of $He$ and $O_2$ gases at $27\,^{\circ}C$ and $760\, torr$ pressure is $0.543\, g\, dm^{-3}$. Calculate the percentage by mass of $He$ in the mixture.

The total pressure in a container containing a gas and a few drops of water is $830 \, mm \, Hg$. If the temperature of the container is decreased by $1 \%$,what will be the new pressure of the container in $mm \, Hg$? The vapor pressure of water at the two temperatures is $30 \, mm \, Hg$ and $25 \, mm \, Hg$ respectively.

At $100\,^\circ\text{C}$ and $1 \, \text{atm}$ pressure,if the density of liquid water is $1.0 \, \text{g cm}^{-3}$ and the density of water vapor is $0.0006 \, \text{g cm}^{-3}$,then the volume occupied by water molecules in $1 \, \text{L}$ of steam is ............. $\text{cm}^3$.