Question

Is the molar volume a physical or chemical property?

Answer 1

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.)

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Molar volume is sometimes labeled `barV = V/n`, where `V` is the volume in `"L"` and `n` is the `"mol"`s of substance. It is the volume occupied by `"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 `"g/mol"`), you can find the `"mol"`s, which allows you to find the molar volume.

EXAMPLE

If you have a volume of `"116 mL"` of ethanol (`"EtOH"`), and you acquire its mass as `"92.136 g"`, then convert to `"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"`

`=` `"0.058 L/mol"`

`=` `color(blue)("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.)