The gas equation $PV = nRT$ is obeyed by:

State Charles's Law.

At constant pressure,the temperature of $20 \ L$ of helium gas is increased from $100 \ K$ to $300 \ K$. What will be the change in volume in $L$?

Find the temperature in $^\circ C$ for a $6.4 \ g$ $O_2$ gas filled in a $200 \ mL$ vessel having pressure $50 \ bar$. $[R = 8.314 \times 10^{-2} \ bar \ L \ K^{-1} \ mol^{-1}]$ (in $^\circ C$)

$34.05 \ mL$ of phosphorus vapor weighs $0.0625 \ g$ at $546 \ ^oC$ and $0.1 \ bar$ pressure. What is the molar mass of phosphorus (in $g/mol$)?

At $273\,K$,$Pd$ vs $P$ is plotted for various gases $1, 2, 3, 4$. Assuming ideal behaviour for four gases $N_2, He, CO_2$ & $H_2$. The correct combination is [$P$ denotes pressure in atmosphere & $d$ denotes density in $g/L$]