# Is the molar volume a physical or chemical property?

Jun 26, 2016

Well, since you can observe it without changing the composition or form of the matter, it's a physical property.

(In fact, if you do change the form of the matter, the molar volume changes, so that further demonstrates its physical nature.)

Molar volume is sometimes labeled $\overline{V} = \frac{V}{n}$, where $V$ is the volume in $\text{L}$ and $n$ is the $\text{mol}$s of substance. It is the volume occupied by $\text{1 mol}$ of the substance.

As long as you can measure the volume, and you know the mass and what substance you're looking at (so you can use its molar mass in $\text{g/mol}$), you can find the $\text{mol}$s, which allows you to find the molar volume.

EXAMPLE

If you have a volume of $\text{116 mL}$ of ethanol ($\text{EtOH}$), and you acquire its mass as $\text{92.136 g}$, then convert to $\text{mol}$s and you have a pure molar volume of:

color(blue)(barV_"EtOH"^"*") = "0.116 L"/(92.136 cancel"g") xx (46.068 cancel"g")/"mol"

$=$ $\text{0.058 L/mol}$

$=$ $\textcolor{b l u e}{\text{58.0 mL/mol}}$

(Do keep in mind that a real liquid would have a different pure molar volume than a partial molar volume in a mixture, if we didn't assume volumes were additive.)