# Calculate molar volume of gas

## Homework Statement

It's not an homework question. I'm trying to figure out this problem, but don't have any idea...

The question is, if 3.0 moles of gas has a volume of 66 L, then what is the molar volume of this gas?

I did like, 22.4 L * 1 atm / 273 K = 66 L * 1 atm / x, but what do I do with 3.0 moles?

## The Attempt at a Solution

danago
Gold Member
Whats the definition of molar volume?

I think you will find you are over complicating this

Molar volume is literally "volume per mole". If you have 3 moles and it occupies 66L, then the volume per mole is ... ?

That number you are using, 22.4, is the molar volume of an ideal gas at STP (spherical particles with no intermolecular interactions).

Last edited:
epenguin
Homework Helper
Gold Member
The molar volume is just the volume occupied by a mole of the substance in the gaseous state. So if 3 moles occupies 66 L the molar volume is just 22 L, simples!

Now you may be getting confused with already having known from somewhere that it is 22.4 L - the figure usually given. I don't know where the figures you gave came from but I can think of three possible reasons for the non-correspondence:

1 Where you got it from was content with a quite approximate figure - it's still right to within 2% after all;

2 22.4 L is at standard pressure (1 atm) and temperature (0°C or 25°C). Maybe this came from a volume under some other conditions;

3 It was a quite far from 'perfect' gas, maybe CO2 or something.