Molar Volume of a Gas

CALCULATIONS BASED ON FORMULAE

7.6 - Molar Volume of a Gas

When the molar mass of ANY gas is divided by the density of gas at STP, the value 22.4 is obtained.

Here are some examples:

Gas Molar Mass (g/mole) Density at STP (g/L) Molar Mass/Density (L/mole)

N₂, nitrogen gas 28.014 1.25 22.4

O₂, oxygen gas 31.998 1.43 22.4

CH₄, methane gas 16.043 0.714 22.4

CO₂, carbon dioxide 44.009 1.96 22.4

H₂, hydrogen gas 2.015 0.090 22.4

Ar, argon gas 39.948 1.78 22.4

Gas	Molar Mass (g/mole)	Density at STP (g/L)	Molar Mass/Density (L/mole)
N₂, nitrogen gas	28.014	1.25	22.4
O₂, oxygen gas	31.998	1.43	22.4
CH₄, methane gas	16.043	0.714	22.4
CO₂, carbon dioxide	44.009	1.96	22.4
H₂, hydrogen gas	2.015	0.090	22.4
Ar, argon gas	39.948	1.78	22.4

Let's take a look what the units of "22.4" is by dimensional analysis (see Section 1.4).

'22.4' has units of liter/mole. This quantity is known as the molar volume of a gas at STP. When 1 mole of gas is at 0oC and 1 atm (or STP condition), the volume that the gas occupies is always 22.4 liter.

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