A-Level Chemistry Year 2: Acids, Bases, Buffers and pH Calculations | A-Level 化学第二年：酸、碱、缓冲溶液与 pH 计算

📚 A-Level Chemistry Year 2: Acids, Bases, Buffers and pH Calculations | A-Level 化学第二年：酸、碱、缓冲溶液与 pH 计算

In Year 2 chemistry, the study of acids, bases, buffers and pH calculations forms a central part of physical chemistry. These ideas connect equilibrium theory with practical laboratory skills and are essential for understanding many reactions in aqueous solution.

在化学第二年，酸、碱、缓冲溶液和 pH 计算的学习构成物理化学的核心部分。这些概念将平衡理论与实验技能联系起来，对于理解水溶液中许多反应至关重要。

1. The Brønsted-Lowry Theory of Acids and Bases | 布朗斯特-劳里酸碱理论

According to the Brønsted-Lowry theory, an acid is a proton donor and a base is a proton acceptor. A proton is represented by H⁺.

根据布朗斯特-劳里理论，酸是质子给体，碱是质子受体。质子用 H⁺ 表示。

When an acid donates a proton, the species left behind is its conjugate base. Similarly, when a base accepts a proton, it forms its conjugate acid. Each acid-base reaction involves two conjugate acid-base pairs.

当酸给出质子后，剩下的物种就是其共轭碱。类似地，当碱接受质子后，就形成其共轭酸。每个酸碱反应都包含两对共轭酸碱对。

• HCl + H₂O → H₃O⁺ + Cl⁻; HCl is an acid and Cl⁻ is its conjugate base.
• HCl + H₂O → H₃O⁺ + Cl⁻；HCl 是酸，Cl⁻ 是其共轭碱。
• NH₃ + H₂O ⇌ NH₄⁺ + OH⁻; NH₃ is a base and NH₄⁺ is its conjugate acid.
• NH₃ + H₂O ⇌ NH₄⁺ + OH⁻；NH₃ 是碱，NH₄⁺ 是其共轭酸。

2. The Ionic Product of Water, Kw | 水的离子积 Kw

Pure water undergoes slight self-ionisation: H₂O ⇌ H⁺ + OH⁻. The equilibrium constant for this process is called the ionic product of water, Kw.

纯水会发生轻微的自电离：H₂O ⇌ H⁺ + OH⁻。该过程的平衡常数称为水的离子积 Kw。

Kw = [H⁺][OH⁻]

At 298 K, Kw = 1.0 × 10⁻¹⁴ mol² dm⁻⁶. Because Kw is an equilibrium constant, its value increases when temperature increases.

在 298 K 时，Kw = 1.0 × 10⁻¹⁴ mol²

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