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

If $P$,$V$,$M$,$T$ and $R$ are pressure,volume,molar mass,temperature and gas constant respectively,then for an ideal gas,the density is given by

$A$ spherical balloon of radius $3 \ cm$ containing helium gas has a pressure of $48 \times 10^{-3} \ bar$. At the same temperature,the pressure of a spherical balloon of radius $12 \ cm$ containing the same amount of gas will be........ $\times 10^{-6} \ bar$.

$A$ truck carrying an oxygen cylinder is coming from $Place \, A$. At $Place \, A$,the gas in the cylinder is at a temperature of $-23 \, ^oC$ and a pressure of $3 \, atm$. When the truck passes through $Place \, B$,the temperature is $30 \, ^oC$. What will be the pressure of the oxygen gas in $atm$?

$n$ moles of an ideal gas at temperature $T$ (in kelvin) occupy $V \ L$ of volume, exerting a pressure of $P$ atmospheres. What is the concentration (in $mol / L$)?