Free Energy of Dissolution · 溶解的自由能
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| dissolution/ˌdɪsəˈluːʃn/ | 溶解 | róng jiě |
Why some salts dissolve and others don't
- Table salt vanishes in water; chalk barely does.
- Both the heat and the disorder of dissolving matter.
- Together they decide whether dissolving is favourable.
- The same free-energy rule applies to dissolving.
为什么有些盐溶解而有些不
- 食盐在水中消失;粉笔几乎不溶。
- 溶解的热和无序都很重要。
- 它们共同决定溶解是否有利。
- 同样的自由能规则适用于溶解。
Dissolving as a process
- Dissolution 溶解 has its own $\Delta G = \Delta H - T\Delta S$.
- If $\Delta G < 0$, dissolving is favourable.
- Both the heat and the entropy of dissolving count.
把溶解看作一个过程
- 溶解有它自己的 $\Delta G = \Delta H - T\Delta S$。
- 若 $\Delta G < 0$,溶解是有利的。
- 溶解的热和熵都算数。
Dissolving is favourable when its $\Delta G$ is... · 当溶解的 $\Delta G$ 为...时，溶解是有利的。
$\Delta G < 0$ means dissolving is favourable. · $\Delta G < 0$ 意味着溶解是有利的。
Whether a salt dissolves favourably depends on... · 盐是否有利地溶解取决于...
$\Delta G$ combines both $\Delta H$ and $\Delta S$. · $\Delta G$ 结合了 $\Delta H$ 和 $\Delta S$。
Disorder favours dissolving
- Dissolving usually increases entropy, as the ordered solid spreads out.
- That positive $\Delta S$ pushes $\Delta G$ toward negative.
- So many salts dissolve even when it costs some heat.
无序有利于溶解
- 溶解通常增大熵,因为有序的固体散开了。
- 那正的 $\Delta S$ 把 $\Delta G$ 推向负。
- 所以许多盐即使要花一些热也会溶解。
Dissolving a solid usually increases the entropy. · 将固体溶解在水中通常会增加熵。
The ordered solid spreads out into solution. · 有序的固体扩散到溶液中。
An ordered solid spreading into solution represents an increase in ____. · 有序的固体扩散到溶液中代表了 ____ 的增加。
Spreading out raises the entropy. · 扩散提高了熵。
The heat can go either way
- Some salts release heat as they dissolve; others absorb it.
- An endothermic dissolving can still be favourable if entropy wins.
- The balance of the two sets $\Delta G$.
热可以是任一方向
- 有些盐溶解时放热;有些吸热。
- 吸热的溶解若熵占上风,仍可以是有利的。
- 两者的平衡决定 $\Delta G$。
An endothermic dissolving can still be favourable if... · 吸热溶解仍可能是有利的，如果...
A large $T\Delta S$ can overcome a positive $\Delta H$. · 大的 $T\Delta S$ 可以克服正的 $\Delta H$。
A salt dissolves endothermically ($\Delta H > 0$) but with a large entropy gain. Can it still dissolve?
- The positive $T\Delta S$ can overcome the positive $\Delta H$.
- So $\Delta G < 0$ and it dissolves.
一种盐吸热溶解($\Delta H > 0$),但熵增很大。它仍能溶解吗?
- 正的 $T\Delta S$ 可以压过正的 $\Delta H$。
- 所以 $\Delta G < 0$,它溶解。
Will it dissolve? · 它会溶解吗？
Sort each case by whether dissolving is thermodynamically favourable. · 根据溶解是否在热力学上有利对每种情况进行分类。
Raising the temperature strengthens the $T\Delta S$ term, often helping a solid dissolve. · 升高温度会增强 $T\Delta S$ 项，通常有助于固体溶解。
A bigger $T\Delta S$ makes $\Delta G$ more negative. · 更大的 $T\Delta S$ 使 $\Delta G$ 更负。
An endothermic dissolving (which feels cold) can still be favourable if the entropy increase is large enough -- do not assume endothermic means "will not dissolve." Both $\Delta H$ and $\Delta S$ of dissolving matter. And higher temperature strengthens the $T\Delta S$ term, often helping a solid dissolve.
吸热的溶解(摸起来凉)仍可以是有利的,只要熵增足够大——别以为吸热就意味着"不会溶解"。溶解的 $\Delta H$ 和 $\Delta S$ 都很重要。而且更高的温度加强 $T\Delta S$ 项,常帮助固体溶解。
Dissolution obeys $\Delta G = \Delta H - T\Delta S$ like any process. Dissolving usually raises entropy (a positive $\Delta S$ that pushes $\Delta G$ negative), so even an endothermic dissolving can be favourable if that entropy gain is large enough.
溶解像任何过程一样遵守 $\Delta G = \Delta H - T\Delta S$。溶解通常增大熵(正的 $\Delta S$ 把 $\Delta G$ 推向负),所以即使吸热的溶解,只要熵增足够大,也可以有利。