Answer
a) $1500kg$
b) $m=200kg$ enters
Work Step by Step
a) Air consists of 20% oxygen (molecular mass of 32u) and 80% nitrogen (molecular mass of 28u). The average molecular mass of air is $M=\frac{20}{100}(32u)+\frac{80}{100}(28u)=28.8u$.
Using the Ideal Gas Law, $n=\frac{PV}{RT}=\frac{(1.013\times10^5Pa)(1200m^3)}{(8.314)(293.15K)}=4.99\times10^4 mol$
$(4.99\times10^4 mol)(0.0288\frac{kg}{mol})=1500kg$
b) $\Delta V=(3400\times10^{-6})(1200m^3)(-30^oC)=122m^3$
$m=(122m^3)(1.29 kg/m^3)=160kg=200kg$ enters
