Compute gas density from ρ = (P·M) / (R·T) using pressure, molar mass and temperature.
由压强、摩尔质量与温度估算理想气体密度。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Density of an ideal gas | rho = P · M / ( R · T ), with P the pressure and M the molar mass | Derived from the ideal gas law; Atkins PW, de Paula J, Physical Chemistry |
| Ideal gas law | p · V = n · R · T | Clapeyron E. (1834); IUPAC, Quantities, Units and Symbols in Physical Chemistry (Green Book) |
| Molar gas constant | R = 8.314462618 J · mol^-1 · K^-1 (CODATA recommended value) | IUPAC, Quantities, Units and Symbols in Physical Chemistry (Green Book) |
| Trend | Density increases with pressure and decreases with temperature | Atkins PW, de Paula J, Physical Chemistry |
Constants used on this page and their authoritative sources, for verification and citation
| Constant | Value | Unit | Source |
|---|---|---|---|
| Molar gas constant R | 8.314462618 | J·mol⁻¹·K⁻¹ | New SI (derived from exact N_A·k; this page uses 8.314) |
| Standard atmosphere (1 atm) | 101 325 | Pa | ISO 2533 defining value (exact) |
| Mean molar mass of dry air M | 28.96546e-3 | kg·mol⁻¹ | CIPM 2007 recommendation (this page uses 28.97 g/mol) |
| Molar volume of an ideal gas (0 ℃, 1 atm) | 22.41396954 | L·mol⁻¹ | Derived from RT/p (same value in CODATA 2018) |
Note: ρ = PM/RT is the ideal-gas approximation; real gases require the compressibility factor Z, with ρ = PM/(ZRT), and deviations become significant at high pressure or low temperature.