The density of a gaseous compound was found to be 1.23g/dm^3 at 330K and 25.5kPa. find the molar mass?

Question

The density of a gaseous compound was found to be 1.23g/dm^3 at 330K and 25.5kPa. find the molar mass?

Answer 1

at 330K  and 25.5 kPa the volume of a mole is

pV=nRT

V= nRT/P and n=1

V=RT/P = 8.314*330/25.5*10^3=0.108m^3=108L

so 1L = 0.009294mole corresponds to 1.23g

and molar mass 1.23/0.009294=132.3g

Answer 2

PV=nRT <=>PV=(m/MM)*RT  <=>P=(m/V)*(RT/MM) <=> P=d*(RT/MM)

<=> MM=d*R*T/P, where P it's pressure, V it's volume, R it's ideal gases constant, m it's the mass, T it's the temperatue, d it's density,n it's the number of moles and MM it's de Molar mass

so: the molar mass it's(using R=0,082 L atm/ mol K)

MM=1,23*0,082*330/0,252=132,1 g/mol

PS: before the calculus it's necessary to convert Pa to atm.