Named laws
| Law | Relation | Held constant |
|---|---|---|
| Boyle's law | P · V = const | T, n |
| Charles' law | V / T = const | P, n |
| Gay-Lussac's law | P / T = const | V, n |
| Avogadro's law | V / n = const | P, T |
| Combined gas law | P · V / T = const | n |
| Ideal gas law | P V = n R T | — |
Constants and conversions
| R (gas constant) | 8.314 J/(mol·K) = 0.08206 L·atm/(mol·K) |
|---|---|
| Molar volume at STP | 22.414 L/mol (0 °C, 1 atm) |
| Molar volume at NTP | 24.466 L/mol (20 °C, 1 atm) |
| Standard atmosphere | 101 325 Pa = 1 atm = 760 mmHg = 14.696 psi |
| Temperature scales | T(K) = T(°C) + 273.15 |
Real-gas corrections
| Compressibility factor Z | PV = Z · n R T. Z = 1 for ideal, < 1 at moderate P, > 1 at very high P |
|---|---|
| Van der Waals | (P + a n²/V²)(V − nb) = nRT |
| Critical point | Above T_c no amount of pressure liquefies the gas |
Notes
- Ideal gas law is accurate for air at ordinary conditions. Deviations appear near critical points, at high pressure, or for polar gases.
- Partial pressure: P_total = ΣP_i; each component's partial pressure is its mole fraction × total pressure.
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