Question

A sample of natural gas is $85.2$% methane and $14.8$% ethane by mass. What is the density of this mixture at ${18}^{\circ }C$ and $748mmHg$?

Answer 1

Molecular mass of mixture is:
$M=\frac{85.2}{100}\times 6+\frac{14.8}{100}\times 30=13.632+4.44=18.07$

$PM=dRT$

$d=\frac{PM}{RT}=\frac{748}{760}\times \frac{18.07}{0.0821\times 291}=0.74g{L}^{-1}$