What is the density of carbon monoxide at $STP$ in $g \, L^{-1}$?

To an evacuated vessel with a movable piston under an external pressure of $1 \ atm$,$0.1 \ mol$ of $He$ and $1.0 \ mol$ of an unknown compound (vapour pressure $0.68 \ atm$ at $0^{\circ} C$) are introduced. Considering ideal gas behaviour,the total volume (in litres) of the gases at $0^{\circ} C$ is close to:

$16 \, g$ of oxygen and $3 \, g$ of hydrogen are mixed and kept at $760 \, mm$ pressure and $0 \, ^oC$. The total volume occupied by the mixture will be nearly

$100 \, g$ of an ideal gas is kept in a cylinder of $416 \, L$ volume at $27^{\circ} C$ under $1.5 \, bar$ pressure. The molar mass of the gas is $.... \, g \, mol^{-1}$. (Nearest integer) (Given : $R = 0.083 \, L \, bar \, K^{-1} \, mol^{-1}$)

If $500 \ cm^3$ of hydrogen gas is at a pressure of $760 \ mm$ and a temperature of $300 \ K$,what is the number of moles?

State Charles' law in brief.