Molar Volume of a Gas
Because gases do not have definate volume (that is, they can be compressed or expanded) there is no volume that a mole of gas occupies.
However, if we assume that the gas is at STP, we can state that...
1 mole of gas at STP occupies 22.4 L
At other temperatures and pressures the molar volume will vary and can be calculated using the Ideal Gas Law.