One mole of any ideal gas fills the same volume at the same temperature and pressure. From PV = nRT: V = 1 × 0.0821 × 273 ÷ 1 = 22.4 L.
Value of Vₘ in different units
| Value | Use it when |
|---|---|
| 22.4 L mol⁻¹ | Old STP: 273 K and 1 atm. Still the usual NCERT and NEET value. |
| 22.7 L mol⁻¹ | IUPAC STP: 273 K and 1 bar. |
| 24.5 L mol⁻¹ | Room conditions: 298 K and 1 atm. |
Formulas that use Vₘ
- Moles of gas = V/22.4 (at STP)
- PV = nRT
Other constants
- Gas constant (R): 8.314 J mol⁻¹ K⁻¹
- Planck's constant (h): 6.626 × 10⁻³⁴ J s
- Avogadro's number (Nₐ): 6.022 × 10²³ mol⁻¹
- Speed of light (c): 3 × 10⁸ m/s
- Charge of an electron (e): 1.602 × 10⁻¹⁹ C
- Mass of an electron (mₑ): 9.109 × 10⁻³¹ kg
- Mass of a proton (mₚ): 1.673 × 10⁻²⁷ kg
- Mass of a neutron (mₙ): 1.675 × 10⁻²⁷ kg
- Universal gravitational constant (G): 6.674 × 10⁻¹¹ N m² kg⁻²
- Acceleration due to gravity (g): 9.8 m/s²
- Boltzmann constant (k): 1.381 × 10⁻²³ J/K
- Faraday constant (F): 96 485 C/mol
- Permittivity of free space (ε₀): 8.854 × 10⁻¹² C² N⁻¹ m⁻²
- Permeability of free space (μ₀): 4π × 10⁻⁷ T m/A
- Rydberg constant (R): 1.097 × 10⁷ m⁻¹
- Stefan–Boltzmann constant (σ): 5.67 × 10⁻⁸ W m⁻² K⁻⁴
- Wien's constant (b): 2.898 × 10⁻³ m K
- Bohr radius (a₀): 0.529 Å
- Molar volume of a gas at STP (Vₘ): 22.4 L/mol
The full list, searchable, is on the physical constants page.
Questions students ask
What is the value of molar volume of a gas at STP?
Vₘ = 22.4 L/mol. In other units: 22.4 L mol⁻¹; 22.7 L mol⁻¹; 24.5 L mol⁻¹.
What is Vₘ in physics and chemistry?
One mole of any ideal gas fills the same volume at the same temperature and pressure. From PV = nRT: V = 1 × 0.0821 × 273 ÷ 1 = 22.4 L.
Which value of Vₘ should I use?
22.4 L mol⁻¹: Old STP: 273 K and 1 atm. Still the usual NCERT and NEET value. 22.7 L mol⁻¹: IUPAC STP: 273 K and 1 bar. 24.5 L mol⁻¹: Room conditions: 298 K and 1 atm.