Gibbs Free Energy and Thermodynamic Favorability · 吉布斯自由能与热力学倾向性
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| Gibbs free energy/ɡɪbz friː ˈenədʒi/ | 吉布斯自由能 | jí bù sī zì yóu néng |
Will it happen on its own?
- Some reactions run by themselves; others need a constant push.
- Two factors decide it: heat released and disorder created.
- A single number combines them into a verdict.
- Its sign tells you whether nature will do it for free.
它会自发发生吗?
- 有些反应自己就进行;有些需要持续的推动。
- 两个因素决定它:放出的热和产生的无序。
- 一个数把它们合成一个判决。
- 它的符号告诉你大自然会不会免费去做。
The free-energy equation
- Gibbs free energy 吉布斯自由能 combines enthalpy and entropy:
- Here $T$ is the temperature in kelvin.
自由能方程
- 吉布斯自由能把焓和熵结合起来:
- 这里 $T$ 是用开尔文表示的温度。
With $\Delta H = -100\ \text{kJ}$, $T = 300\ \text{K}$, $\Delta S = 0.2\ \text{kJ/K}$, find $\Delta G$ (in kJ). · 给定 $\Delta H = -100\ \text{kJ}$、$T = 300\ \text{K}$、$\Delta S = 0.2\ \text{kJ/K}$，求 $\Delta G$（单位为 kJ）。
$\Delta G = \Delta H - T\Delta S = -100 - (300)(0.2) = -160\ \text{kJ}$.
In $\Delta G = \Delta H - T\Delta S$, the temperature must be in... · 在 $\Delta G = \Delta H - T\Delta S$ 中，温度必须是...
Thermodynamic equations need an absolute temperature in kelvin. · 热力学方程需要开尔文温标下的绝对温度。
Negative means favourable
- $\Delta G < 0$ means the reaction is thermodynamically favourable.
- $\Delta G > 0$ means it is not favourable on its own.
- $\Delta G = 0$ means the system is at equilibrium.
负号意味着有利
- $\Delta G < 0$ 意味着反应在热力学上有利。
- $\Delta G > 0$ 意味着它自身不利。
- $\Delta G = 0$ 意味着系统处于平衡。
A reaction is thermodynamically favourable when $\Delta G$ is... · 当 $\Delta G$ 为...时，反应在热力学上是有利的。
$\Delta G < 0$ means the reaction is favourable. · $\Delta G < 0$ 意味着反应是有利的。
When $\Delta G = 0$, the system is at ____. · 当 $\Delta G = 0$ 时，系统处于 ____。
$\Delta G = 0$ marks equilibrium. · $\Delta G = 0$ 标志着平衡。
Temperature can flip it
- Exothermic plus more disorder is favourable at all temperatures.
- Endothermic plus less disorder is never favourable.
- The other two cases flip with temperature.
温度能把它翻转
- 放热加上更多无序,在所有温度下都有利。
- 吸热加上更少无序,永远不利。
- 另外两种情形随温度翻转。
A reaction with $\Delta H < 0$ and $\Delta S > 0$ is favourable... · 具有 $\Delta H < 0$ 和 $\Delta S > 0$ 的反应是有利的...
Both terms make $\Delta G$ negative regardless of $T$. · 无论$\Delta G$是什么，这两个术语都使$T$为负。
A reaction has $\Delta H < 0$ and $\Delta S > 0$. Is it favourable?
- Both terms push $\Delta G$ negative.
- So it is favourable at every temperature.
一个反应 $\Delta H < 0$ 且 $\Delta S > 0$。它有利吗?
- 两项都把 $\Delta G$ 推向负。
- 所以它在每个温度下都有利。
Free energy versus temperature · 自由能与温度的关系
ΔG = ΔH - TΔS is a straight line in temperature. Where it crosses zero, the reaction turns favourable. · ΔG = ΔH - TΔS 在温度下呈直线关系。在该直线穿过零点处，反应变为有利。
A thermodynamically favourable reaction is always fast. · 热力学上有利的反应总是快速的。
Favourability is about direction, not speed; kinetics sets the rate. · 倾向性关乎方向，而非速度；动力学决定速率。
"Favourable" ($\Delta G < 0$) means thermodynamically allowed, not fast -- kinetics decides the speed. The temperature is in kelvin in $\Delta G = \Delta H - T\Delta S$. And the $T\Delta S$ term grows with temperature, so heating can flip the sign of $\Delta G$.
"有利"($\Delta G < 0$)意味着热力学上允许,而不是快——速度由动力学决定。$\Delta G = \Delta H - T\Delta S$ 中温度用开尔文。而且 $T\Delta S$ 项随温度增大,所以加热能把 $\Delta G$ 的符号翻转。
Gibbs free energy $\Delta G = \Delta H - T\Delta S$ combines heat and disorder into one verdict: $\Delta G < 0$ is thermodynamically favourable, $> 0$ is not, and $= 0$ is equilibrium. Because of the $T\Delta S$ term, temperature can flip the sign for two of the four cases.
吉布斯自由能 $\Delta G = \Delta H - T\Delta S$ 把热和无序合成一个判决:$\Delta G < 0$ 在热力学上有利,$> 0$ 不利,$= 0$ 是平衡。由于 $T\Delta S$ 项,温度能为四种情形中的两种翻转符号。