Determination of molar mass
Exercise 3
A gaseous substance has at $765\;mmHg$ and $18^oC$ a volumetric mass of $2.10\frac{g}{L} $.
Calculate the molar mass.
Let's take $1 \; L$ of that gas. ie $2.10 \; g$ :
$p$ $=$ $\frac{765}{760}\; atm$
$n$ $=$ $\frac{p\;V}{R\; T} $ =
$\frac{765\; 1 }{760\; 0.082 \; 291.15}$ =
$0.042$
$M$ $=$ $\frac{m}{n}$ =
$\frac{2.10}{0.042}$ =
$50\; \frac{g}{mol}$