If in a given container there are $N$ number of molecules,then what will be the number of moles?

At a constant temperature,by what percentage $(\%)$ must the pressure of a given mass of gas be increased so that its volume decreases by $10\%$ (in $.1$)?

$A$ cylinder contains $10\, kg$ of gas at a pressure of $10^7\, N/m^2$. The quantity of gas taken out of the cylinder,if the final pressure is $2.5 \times 10^6\, N/m^2$,will be ..... $kg$ (Temperature of the gas is constant).

The equation of state for $2 \ g$ of oxygen at a pressure $P$ and temperature $T$,when occupying a volume $V$,will be:

At $NTP$,the mass of one litre of air is $1.293 \; g$. The value of the specific gas constant will be ...... $J/(K \cdot g)$.

$O_2$ gas is filled in a cylinder. If the pressure is doubled and the temperature is quadrupled,what will be the factor by which the density changes?