Library / Foundations: Chemistry / FCH-07
Foundations: Chemistry
Volume of a gas
Volume occupied by a number of moles of gas at room temperature and pressure.
- Ref
- FCH-07
- Rev
- v1
- Field
- Foundations: Chemistry
- Result
- V [dm³]
Vm is the molar volume: about 24 dm³/mol at room temperature and pressure (20 °C, 1 atm) and 22.4 dm³/mol at standard temperature and pressure (0 °C, 1 atm).
One mole of any gas takes up the same volume under the same conditions, so volume is just moles times that fixed amount.
Calculator
- Volume in cm³2,400 cm³
- Moles in 1 dm³0.04167 mol
What drives the result
Each variable is moved across its typical range while the others stay at the values above. The longest bar is the key driver.
- 0.100 mol of any gas at RTP occupies 2.4 dm³, whether it is hydrogen or carbon dioxide.
- Real volumes depend on temperature and pressure; use the ideal gas law when conditions differ.
Chart data as tables
Ranked variables
| Variable | Typical range | Lowest result | Highest result | Swing (dm³) | Local step | Change in result |
|---|---|---|---|---|---|---|
| n Amount of gas | 0.001 to 10 mol | 0.024 | 240 | 240 | +10% | +10 % |
| Vm Molar volume | 22.4 to 25 dm³/mol | 2.24 | 2.5 | 0.26 | +10% | +10 % |
Sweep of Amount of gas
| Amount of gas (mol) | Gas volume (dm³) |
|---|---|
| 0.001 | 0.024 |
| 0.003162 | 0.07589 |
| 0.01 | 0.24 |
| 0.03162 | 0.7589 |
| 0.1 | 2.4 |
| 0.3162 | 7.589 |
| 1 | 24 |
| 3.162 | 75.89 |
| 10 | 240 |
Sweep one variable
Variables and how each one contributes
Gas volume
What the equation gives you. Everything else feeds it.
Amount of gas
Moles of gas. Directly proportional.
Molar volume
24 at RTP; 22.4 at STP. Directly proportional.
Worked example with the values above
- Vm = 24 dm³/mol.
- V = n × Vm = 0.1 × 24.
- V = 2.4 dm³ (2,400 cm³).
Assumptions and limits
- Ideal gas behaviour.
- Stated temperature and pressure.
Common mistakes
- Using 22.4 at room temperature.
- Giving the answer in cm³ when dm³ is asked.
Statistics and uncertainty
Using 24 instead of 22.4 gives a 7% difference, so state the conditions.
Where it is used
- Gas evolution in reactions.
- Sizing gas storage and vents.
Maths you need
- Moles: n = m / Mr
- Gas laws: volume and conditions