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

If the temperature of a fixed mass of gas is increased by $1\,^{\circ}C$ at constant pressure,what will be the new volume of the gas?

The density of air is higher at sea level. This fact is a practical application of which law?

If the pressure of a gas in a closed vessel increases by $0.4\%$ when heated by $1\,^oC$,its initial temperature is ....... $K$.

The pressure exerted by a non-reactive gaseous mixture of $6.4 \ g$ of methane and $8.8 \ g$ of carbon dioxide in a $10 \ L$ vessel at $27^{\circ} C$ is .............$kPa$.
(Round off to the Nearest Integer).
[Assume gases are ideal,$R = 8.314 \ J \ mol^{-1} K^{-1}$
Atomic masses $: C = 12.0 \ u, H = 1.0 \ u, O = 16.0 \ u]$

An ideal gas weighing $9.0 \ g$ occupies a volume of $8.2 \ L$ at $300 \ K$ and $1 \ atm$ pressure. The molar mass of the gas is .....