含义Meaning
衡量真实气体偏离理想的程度：Z = 1 为理想；Z < 1 吸引占优；Z > 1 排斥占优。
Measures deviation from ideality: Z = 1 ideal, Z < 1 attractions dominate, Z > 1 repulsions dominate.
符号说明Symbols
| 符号Symbol | 含义 Meaning | 单位 Unit |
|---|---|---|
| \(Z\) | 压缩因子compressibility factor | 1 |
| \(V_m\) | 摩尔体积molar volume | m³·mol⁻¹ |
推导Derivation
理想气体 \(pV_m = RT\)，故定义 \(Z = pV_m/RT\) 作为偏差量度。
Since \(pV_m = RT\) for ideal gases, \(Z = pV_m/RT\) measures deviation.
对比态原理：以 \(p_r = p/p_c\)、\(T_r = T/T_c\) 表示时，不同气体的 Z 近似落在同一组曲线上（通用压缩因子图）。
Corresponding states: plotted against \(p_r = p/p_c\), \(T_r = T/T_c\), different gases fall on nearly the same curves (generalised chart).
玻意耳温度 \(T_B\) 时第二维里系数为零，Z 在低压区近似为 1；范德华气体 \(T_B = a/(Rb)\)。
At the Boyle temperature the second virial coefficient vanishes; for a van der Waals gas \(T_B = a/(Rb)\).
适用条件与局限Assumptions & limitations
对比态原理对极性、缔合分子（H₂O、NH₃）和量子气体（H₂、He）误差较大，需引入偏心因子 ω。
Corresponding states works poorly for polar/associating molecules and quantum gases; add the acentric factor ω.