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.

If $1 \ g$ of $CH_4$ gas effuses through a fine hole in $100 \ s$,how many grams of $SO_2$ gas will effuse in $100 \ s$ under the same conditions of temperature and pressure?

In a closed flask of $5 \ L$,$1.0 \ g$ of $H_2$ is heated from $300 \ K$ to $600 \ K$. Which statement is not correct?

For one mole of an ideal gas,increasing the temperature from $10^{\circ} C$ to $20^{\circ} C$:

Two flasks $A$ and $B$ have equal volumes. $A$ is maintained at $300 \ K$ and $B$ at $600 \ K$. Equal masses of $H_2$ and $CO_2$ are taken in flasks $A$ and $B$ respectively. Find the ratio of total $K.E.$ of gases in flask $A$ to that of $B$.

What is the ratio of kinetic energies of $3 \ g$ of hydrogen and $4 \ g$ of oxygen at a certain temperature?