\[\Delta_rG^\circ = -RT\ln K^\circ,\qquad K^\circ = e^{-\Delta_rG^\circ/RT}\]
含义Meaning
把反应的标准吉布斯能与平衡常数联系起来。25 °C 时 ΔG° 每变化 5.7 kJ/mol，K 变化 10 倍；ΔG° < −30 kJ/mol 时反应几乎完全，> +30 kJ/mol 时几乎不进行。
Links standard Gibbs energy to K. At 25 °C each 5.7 kJ/mol changes K tenfold; ΔG° below −30 kJ/mol means essentially complete reaction, above +30 almost none.
符号说明Symbols
| 符号Symbol | 含义 Meaning | 单位 Unit |
|---|---|---|
| \(\Delta_rG^\circ\) | 标准反应吉布斯能standard reaction Gibbs energy | kJ·mol⁻¹ |
推导Derivation
反应等温式 \(\Delta_rG = \Delta_rG^\circ + RT\ln Q\)。
Reaction isotherm.
平衡时 \(\Delta_rG = 0\)、Q = K，得 \(\Delta_rG^\circ = -RT\ln K\)。
At equilibrium ΔrG = 0 and Q = K.
适用条件与局限Assumptions & limitations
K° 是无量纲的热力学平衡常数；与 Kc、Kp 换算需除以标准浓度 1 mol/L 或标准压强 1 bar。
K° is dimensionless; convert Kc, Kp by dividing by c° or p°.
ΔG° 判断的是标准态下的方向；实际方向看 ΔG（含 Q）。
ΔG° gives direction only under standard conditions.