📚 AQA A-Level Chemistry 1.8 Thermodynamics: Enthalpy, Entropy and Gibbs Free Energy | AQA A-Level 化学 1.8 热力学：焓、熵与吉布斯自由能
Thermodynamics connects enthalpy changes, entropy and reaction feasibility. For AQA, you must be able to recall standard definitions, build Hess and Born-Haber cycles, calculate entropy and Gibbs free energy changes, and explain limitations of feasibility predictions.
热力学将焓变、熵和反应可行性联系起来。在 AQA 考试中，你需要记住标准定义、构建盖斯与玻恩-哈伯循环、计算熵变和吉布斯自由能变，并解释可行性预测的局限性。
1. Standard Enthalpy Changes and Definitions | 标准焓变与定义
Standard conditions are 100 kPa pressure, 298 K temperature and solutions at 1 mol dm⁻³. The standard state is the most stable physical state under these conditions.
标准条件是 100 kPa 压强、298 K 温度以及 1 mol dm⁻³ 的溶液。标准状态是指在这些条件下最稳定的物理状态。
Standard enthalpy of formation (ΔHf°) is the enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions.
标准生成焓（ΔHf°）是在标准条件下，由标准状态的元素生成 1 mol 化合物时的焓变。
Standard enthalpy of atomisation (ΔHat°) is the enthalpy change when one mole of gaseous atoms is formed from the element in its standard state.
标准原子化焓（ΔHat°）是由标准状态的元素生成 1 mol 气态原子时的焓变。
First ionisation energy is the enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
第一电离能是从 1 mol 气态原子中移除 1 mol 电子形成 1 mol 气态 1+ 离子时的焓变。
First electron affinity is the enthalpy change when one mole of electrons is added to one mole of gaseous atoms to form one mole of gaseous 1− ions.
第一电子亲和能是向 1 mol 气态原子中加入 1 mol 电子形成 1 mol 气态 1− 离子时的焓变。
e⁻ → O²⁻(g), is endothermic because the incoming electron is repelled by the negative ion.
第二电子亲和能，如 O(g) + e⁻ → O²⁻(g)，是吸热的，因为进入的电子受到负离子的排斥。
Lattice enthalpy of formation is the enthalpy change when one mole of a solid ionic lattice is formed from its gaseous ions.
晶格生成焓是由气态离子生成 1 mol 固态离子晶格时的焓变。
Standard enthalpy of hydration is the enthalpy change when one mole of gaseous ions dissolves in water to form one mole of aqueous ions.
标准水合焓是 1 mol 气态离子溶于水形成 1 mol 水合离子时的焓变。
Standard enthalpy of solution is the enthalpy change when one mole of solute dissolves in water to form a very dilute solution.
标准溶解焓是 1 mol 溶质溶于水形成极稀溶液时的焓变。
2. Hess's Law and Enthalpy Cycles | 盖斯定律与焓变循环
Hess's law states that the total enthalpy change for a reaction depends only on the initial and final states and is independent of the route taken.
盖斯定律指出，反应
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