Moles and Gas Volumes [H]

This lesson covers the relationship between moles and gas volumes as required by the AQA GCSE Chemistry specification (4.3.3). This is Higher Tier only content. You need to understand the concept of molar volume, be able to calculate the volume of a gas from the number of moles (and vice versa), and use this in reacting mass and gas volume calculations.

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Molar Volume of a Gas

At room temperature and pressure (RTP) — defined as 20 degrees Celsius and 1 atmosphere (1 atm) — one mole of any gas occupies a volume of 24 dm3 (or 24,000 cm3). This is called the molar volume.

Condition	Temperature	Pressure	Molar Volume
RTP (room temperature and pressure)	20 degrees C	1 atm	24 dm3/mol (24,000 cm3/mol)

This value applies to all gases, regardless of the identity of the gas. One mole of hydrogen (H2), one mole of oxygen (O2), one mole of carbon dioxide (CO2), and one mole of chlorine (Cl2) all occupy 24 dm3 at RTP.