Answer
$N=30.59 kmol$
$m=122.36kg$
Work Step by Step
First we calculate the volume:
$V=\frac{4\pi r^3}{3}=\frac{4\pi*(\frac{9m}{2})^3}{3}=381.7m^3$
From the ideal gas law:
$N=\frac{PV}{R_{u}T}=\frac{200kPa*381.7m^3}{8.314\frac{kPam^3}{kmolK}*(27+273.15)K}=30.59 kmol$
$m=NM=30.59 kmol*4\frac{kg}{kmol}=122.36kg$
