The use of hot air balloons for sports and meteorological observations is based on which of the following laws?

At $25 \, ^\circ C$,the density of oxygen gas is $1.458 \, mg/L$ at $1 \, atm$ pressure. What will be the pressure of oxygen gas if the density is doubled?

When a graph of the product of pressure and volume $(PV)$ versus pressure $(P)$ is plotted for a fixed amount of gas at a constant temperature,what type of line is obtained?

$A$ monoatomic ideal gas,initially at temperature $T_1$,is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature $T_2$ by releasing the piston suddenly. $L_1$ and $L_2$ are the lengths of the gas columns before and after the expansion,respectively. The ratio $\frac{T_2}{T_1}$ is:

$A$ gas has a volume of $3.4 \ L$ at $298 \ K$. What is the final temperature if the volume of gas increases to $6.8 \ L$ (in $K$)?

$A$ gas occupies a volume of $300 \, cc$ at $27 \, ^\circ C$ and $620 \, mm$ pressure. The volume of gas at $47 \, ^\circ C$ and $640 \, mm$ pressure is......$cc$