$A$ certain mass of a gas occupies a volume of $2 \ dm^{3}$ at $STP$. At what temperature will the volume of the gas become double,keeping the pressure constant (in $^{\circ} C$)?

The value of the gas constant $R$ depends on which of the following?

$N_2$ gas at $100 \, kPa$ pressure is filled in a $1 \, L$ flask and $O_2$ gas at $320 \, kPa$ pressure is filled in another $3 \, L$ flask. If both flasks are connected,what will be the resultant pressure in $kPa$?

At $200 \ K$,an ideal gas $(X)$ present in a $1 \ L$ flask has a concentration of $1 \ mol \ L^{-1}$. At the same temperature,$0.1 \ mol$ of $X$ is added into the vessel. What is the final pressure of the gas in $atm$?
(Given $R = 0.082 \ L \ atm \ mol^{-1} \ K^{-1}$)

Use of hot air balloons in sports and meteorological observations is an application of

The volume of a given amount of gas at $27^{\circ} C$ at constant pressure is $420 \ cm^3$. If the temperature is reduced by $20^{\circ} C$ at constant pressure, what will be the volume of the gas (in $cm^3$)?