22.414
L
24.79
L
1.2492
g/L
6.022
×10²³
22.414
L
24.79
L
1.2492
g/L
6.022
×10²³
The STP Calculator converts between moles and volume for ideal gases at Standard Temperature and Pressure (STP: 0°C, 1 atm) and Standard Ambient Temperature and Pressure (SATP: 25°C, 1 bar). Enter the number of moles and molar mass to find the gas volume, density, and number of molecules at standard conditions.
Standard conditions are fundamental reference points in chemistry. At STP, one mole of any ideal gas occupies exactly 22.414 liters. This molar volume allows easy conversion between mass, moles, and volume in gas-phase calculations and is one of the most commonly used values in general chemistry.
At STP (273.15 K, 1 atm = 101.325 kPa), the molar volume of an ideal gas is derived from PV=nRT:
$$V_m = \frac{RT}{P} = \frac{0.08206 \times 273.15}{1} = 22.414 \text{ L/mol}$$
At SATP (298.15 K, 1 bar = 100 kPa), the IUPAC standard:
$$V_m = \frac{RT}{P} = \frac{0.08314 \times 298.15}{1} = 24.790 \text{ L/mol}$$
The total volume is simply:
$$V = n \times V_m$$
Gas density at STP depends on molar mass:
$$\rho = \frac{M}{V_m} = \frac{M}{22.414} \text{ g/L}$$
The number of molecules is:
$$N = n \times N_A = n \times 6.022 \times 10^{23}$$
The volume at STP gives the space the gas occupies at 0°C and 1 atm. The SATP volume is slightly larger because the temperature is higher (25°C) and pressure slightly lower (1 bar vs 1 atm). The density depends on the molar mass — heavier gases are denser. The molecule count gives the absolute number of particles, useful for understanding the enormous scale of chemical quantities.
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Results
One mole of N₂ (28 g) occupies 22.414 L at STP with a density of 1.25 g/L. This is very close to the density of air (1.29 g/L at STP) because nitrogen makes up 78% of the atmosphere.
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Results
Five moles of CO₂ (220 g) occupies 112 L at STP. CO₂ is denser than air (1.96 vs 1.29 g/L) because of its higher molar mass (44 vs ~29 g/mol), which is why CO₂ tends to settle in low-lying areas.
STP stands for Standard Temperature and Pressure: 0°C (273.15 K) and 1 atm (101.325 kPa). At these conditions, one mole of an ideal gas occupies 22.414 liters. STP is the traditional reference condition used in chemistry for gas calculations.
SATP stands for Standard Ambient Temperature and Pressure: 25°C (298.15 K) and 1 bar (100 kPa). It is the IUPAC-recommended standard since 1982. The molar volume at SATP is 24.790 L/mol, larger than at STP because the temperature is higher and pressure slightly lower.
It is calculated from PV = nRT: V = (1 mol)(0.08206 L·atm/mol·K)(273.15 K)/(1 atm) = 22.414 L. This value is specific to STP conditions. At different temperatures and pressures, the molar volume changes accordingly.
For ideal gases, yes — 22.414 L/mol. Real gases have slightly different molar volumes due to intermolecular forces. For example: He = 22.434 L, H₂ = 22.433 L, O₂ = 22.392 L, CO₂ = 22.260 L. The deviations are small (within 1%) for most common gases.
Simply divide the volume by the molar volume: n = V/22.414. For example, 11.2 L of gas at STP = 11.2/22.414 = 0.5 mol. This is one of the most useful shortcuts in chemistry for gas stoichiometry problems.
Avogadro's number (Nₐ = 6.022 × 10²³ mol⁻¹) is the number of particles in one mole. At STP, 22.414 L of any ideal gas contains exactly 6.022 × 10²³ molecules. This enormous number illustrates the vast number of molecules in even small amounts of matter.
At STP, gas density (g/L) equals the molar mass divided by 22.414: ρ = M/22.414. Heavier gases are denser: H₂ (0.089 g/L), air (1.29 g/L), CO₂ (1.96 g/L), SF₆ (6.52 g/L). This is why CO₂ and SF₆ sink while H₂ and He rise.
STP provides a standard reference that allows chemists to compare gas measurements and perform stoichiometric calculations consistently. By converting all gas volumes to STP, different experiments can be directly compared regardless of the actual laboratory conditions.
Yes, at STP the molar volume allows direct conversion between liters and moles. For the reaction 2H₂ + O₂ → 2H₂O: at STP, 44.8 L of H₂ reacts with 22.4 L of O₂. Volume ratios equal mole ratios at constant T and P, simplifying calculations.
STP (Standard Temperature and Pressure) is 0°C, 1 atm. NTP (Normal Temperature and Pressure) is 20°C, 1 atm (used mainly in engineering). SATP is 25°C, 1 bar (IUPAC). Each has a different molar volume: STP = 22.414 L, NTP ≈ 24.04 L, SATP = 24.790 L.
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