Standard Temperature and Pressure (STP)
STP is defined as 273.15 K (0°C) and 1 atm (101.325 kPa). At STP, one mole of any ideal gas occupies 22.414 L. The ideal gas law PV = nRT enables conversion between conditions.
Why This Chemistry Calculation Matters
Why: STP provides a standard reference for comparing gas volumes across reactions and conditions. Essential for gas stoichiometry, molar volume calculations, and analytical chemistry.
How: Enter volume, temperature, and pressure (or moles, or mass + molar mass). The calculator applies the combined gas law V_STP = V × (T_STP/T) × (P/P_STP) or molar volume V = n × 22.414 L/mol.
- ●IUPAC and NIST define STP as 273.15 K, 101.325 kPa.
- ●SATP (25°C, 1 bar) gives molar volume ≈ 24.8 L/mol.
- ●Real gases deviate at high P or low T; van der Waals corrects.
Compact Examples
Inputs
⚠️For educational and informational purposes only. Verify with a qualified professional.
🔬 Chemistry Facts
STP = 273.15 K (0°C), 1 atm — IUPAC standard reference.
— IUPAC
22.414 L/mol = R×273.15/1 from ideal gas law.
— CODATA
Gas stoichiometry uses STP to compare volumes across reactions.
— Analytical chem
1 mol ideal gas at STP occupies same volume regardless of identity.
— Avogadro
📋 Key Takeaways
- • STP | 273.15 K (0°C), 1 atm — IUPAC standard reference
- • Molar volume | 22.414 L/mol for any ideal gas at STP
- • Combined gas law | V_STP = V × (T_STP/T) × (P/P_STP)
- • Ideal gas | PV = nRT; assumes negligible molecular volume
Did You Know?
STP differs from SATP (25°C, 1 bar); molar volume at SATP ≈ 24.8 L/mol.
Source: IUPAC
22.414 L/mol comes from R×273.15/1 = 0.082057×273.15.
Source: CODATA
Gas stoichiometry uses STP to compare volumes across reactions.
Source: Analytical chem
Real gases deviate at high P or low T; van der Waals corrects.
Source: Physical chem
NIST and IUPAC both define STP as 273.15 K, 101.325 kPa.
Source: Standards
1 mol ideal gas at STP occupies same volume regardless of identity.
Source: Avogadro
How the STP Calculator Works
Enter volume, temperature, and pressure (or moles, or mass + molar mass). The calculator applies the combined gas law or molar volume to convert to STP conditions.
Volume to STP
V_STP = V × (273.15/T) × (P/1 atm)
Moles to Volume
V = n × 22.414 L/mol
Expert Tips
Use Kelvin
Always convert T to K before applying gas laws.
Pressure Units
Convert to atm (or consistent units) for combined law.
High P / Low T
Ideal gas law less accurate; consider real gas models.
Stoichiometry
Convert gas volumes to moles at STP for balanced equations.
Common Gases at STP
| Gas | Formula | Molar Mass (g/mol) | Density at STP (g/L) |
|---|---|---|---|
| Hydrogen | H_{2} | 2.016 | 0.0899 |
| Helium | ext{He} | 4.003 | 0.1785 |
| Nitrogen | N_{2} | 28.014 | 1.2506 |
| Oxygen | O_{2} | 31.999 | 1.429 |
| Carbon Dioxide | CO_{2} | 44.01 | 1.977 |
| Argon | ext{Ar} | 39.948 | 1.784 |
| Neon | ext{Ne} | 20.18 | 0.9 |
| Methane | ext{CH}₄ | 16.043 | 0.717 |
| Ammonia | NH_{3} | 17.031 | 0.771 |
| Chlorine | Cl_{2} | 70.906 | 3.214 |
| Hydrogen Chloride | ext{HCl} | 36.461 | 1.639 |
| Sulfur Dioxide | SO_{2} | 64.066 | 2.927 |
Frequently Asked Questions
What is STP?
Standard Temperature (273.15 K, 0°C) and Pressure (1 atm, 101.325 kPa). IUPAC reference for gas comparisons.
Why 22.414 L/mol?
From PV=nRT: V/n = RT/P = 0.082057×273.15/1 ≈ 22.414 L/mol at STP.
STP vs SATP?
SATP = 25°C, 1 bar; molar volume ≈ 24.8 L/mol. STP uses 0°C, 1 atm.
When is ideal gas law valid?
Low pressure, moderate temperature. Deviations at high P or near condensation.
How to convert volume to STP?
V_STP = V × (273.15/T) × (P/1) with T in K, P in atm.
Moles from volume at STP?
n = V_STP / 22.414.
What about water vapor?
Correct for partial pressure if gas collected over water.
Key Numbers
📚 Official Sources
⚠️ Disclaimer: Uses IUPAC STP (273.15 K, 1 atm), CODATA gas constant, ideal gas law. For precise work consult IUPAC Gold Book, NIST, and CODATA.