IB Chemistry: Comparison of Major Acid-Base Theories | IB化学：酸碱理论主要学说比较

📚 IB Chemistry: Comparison of Major Acid-Base Theories | IB化学：酸碱理论主要学说比较

Acid–base theories are fundamental to chemistry, yet no single definition explains every reaction. In IB Chemistry, you are expected to understand and apply three major models — Arrhenius, Brønsted–Lowry, and Lewis — and to recognise why each was proposed and where it succeeds or fails.

酸碱理论是化学的基础，但没有任何一个定义能解释所有反应。在IB化学中，你需要理解并运用三大主要模型——阿伦尼乌斯、布仑斯特-劳里和路易斯——并认识到它们各自为何被提出、在何处有效、在何处失效。

1. The Need for Multiple Theories | 1. 多种理论存在的必要性

Early acid–base ideas were based on observable properties such as sour taste, colour changes in dyes, and reaction with carbonates. These observations led to empirical definitions, but they could not explain reactions in non-aqueous solvents or in gases.

早期酸碱概念建立在可观察的性质上，如酸味、染料颜色变化以及与碳酸盐的反应。这些观察产生了经验性定义，但不能解释非水溶剂中或气相中的反应。

As chemists studied more reactions, they realised that acidity and basicity are not absolute properties of substances alone; they depend on the reaction context. This is why multiple theories exist.

随着化学家研究更多反应，他们意识到酸性和碱性并非物质自身的绝对属性，而是取决于反应环境。这正是多种理论并存的原因。

2. Arrhenius Theory | 2. 阿伦尼乌斯理论

In 1887, Svante Arrhenius defined an acid as a substance that produces hydrogen ions (H⁺) in aqueous solution, and a base as a substance that produces hydroxide ions (OH⁻) in aqueous solution.

1887年，斯万特·阿伦尼乌斯将酸定义为在水溶液中产生氢离子（H⁺）的物质，将碱定义为在水溶液中产生氢氧根离子（OH⁻）的物质。

For example, HCl dissolves in water to give H⁺ and Cl⁻, while NaOH gives Na⁺ and OH⁻. The neutralisation reaction is written simply as H⁺ + OH⁻ → H₂O.

例如，HCl溶于水产生H⁺和Cl⁻，而NaOH产生Na⁺和OH⁻。中和反应可简单写为 H⁺ + OH⁻ → H₂O。

HCl(aq) → H⁺(aq) + Cl⁻(aq)

NaOH(aq) → Na⁺(aq) + OH⁻(aq)

This theory is simple and useful for common aqueous solutions, especially in introductary stoichiometry and titration calculations.

该理论简单实用，适用于常见水溶液，尤其是基础化学计量学和滴定计算。

3. Limitations of Arrhenius Theory | 3. 阿伦尼乌斯理论的局限

The Arrhenius theory fails outside water. For example, ammonia acting as a base in water is explained, but much of the reaction happens because NH₃ accepts a proton from water rather than releasing OH⁻ directly.

阿伦尼乌斯理论在水之外失效。例如，氨在水中表现为碱，但该反应实际上是因为NH₃从水中接受质子，而不是直接解离出OH⁻。

Also, many bases that do not contain hydroxide ion, such as ammonia, cannot be classified by the Arrhenius definition.

此外，许多不含氢氧根离子的碱，如氨，无法用阿伦尼乌斯定义归类。

Acidic or basic behaviour is limited to aqueous solution.

酸碱行为仅限于水溶液。
Only one type of base (OH⁻ producer) is allowed.

只允许一种碱（产生OH⁻的物质）。
Cannot explain reactions in liquid ammonia, sulphuric acid, or the gas phase.

无法解释液氨、液态硫酸或气相中的反应。

4. Brønsted–Lowry Theory | 4. 布仑斯特-劳里理论

In 1923, Johannes Brønsted and Thomas Lowry independently defined an acid as a proton (H⁺) donor and a base as a proton acceptor. This definition works in any solvent, not just water.

1923年，约翰内斯·布仑斯特与托马斯·劳里独立将酸定义为质子（H⁺）给予体，将碱定义为质子接受体。该定义适用于任何溶剂，而不仅是水。

In the reaction between ammonia and water, NH₃ accepts a proton from H₂O, so NH₃ is the base and H₂O is the acid.

在氨与水的反应中，NH₃从H₂O获得质子，因此NH₃是碱，H₂O是酸。

NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH⁻(aq)

Here, water is amphiprotic because it can act as both an acid and a base.

这里水是两性物质，因为它既可作为酸也可作为碱。

5. Conjugate Acid–Base Pairs | 5. 共轭酸碱对

A Brønsted–Lowry acid–base reaction always involves two conjugate pairs. When an acid donates a proton, it becomes its conjugate base; when a base accepts a proton, it becomes its conjugate acid.

布仑斯特-劳里酸碱反应始终涉及两对共轭对。当酸失去质子时，变成其共轭碱；当碱获得质子时，变成其共轭酸。

For a general acid HA, the equilibrium is:

对于一般酸HA，平衡可表示为：

HA(aq) + H₂O(l) ⇌ A⁻(aq) + H₃O⁺(aq)

The pair HA/A⁻ is a conjugate pair, and H₃O⁺/H₂O is another conjugate pair.

HA/A⁻是一个共轭对，H₃O⁺/H₂O是另一个共轭对。

Acid	Conjugate Base
HCl	Cl⁻
H₂SO₄	HSO₄⁻
NH₄⁺	NH₃
H₂O	OH⁻

Strong acids have weak conjugate bases, and weak acids have relatively stronger conjugate bases.

强酸的共轭碱很弱，而弱酸的共轭碱相对较强。

6. Amphiprotic Species | 6. 两性物质

An amphiprotic species can donate or accept a proton, meaning it has both a conjugate acid and a conjugate base. Hydrogen carbonate ion (HCO₃⁻) is a classic example.

两性物质既能给出质子也能接受质子，这意味着它既有共轭酸也有共轭碱。碳酸氢根离子（HCO₃⁻）是典型例子。

As an acid: HCO₃⁻(aq) + H₂O(l) ⇌ CO₃²⁻(aq) + H₃O⁺(aq)

作为酸： HCO₃⁻(aq) + H₂O(l) ⇌ CO₃²⁻(aq) + H₃O⁺(aq)

As a base: HCO₃⁻(aq) + H₂O(l) ⇌ H₂CO₃(aq) + OH⁻(aq)

作为碱： HCO₃⁻(aq) + H₂O(l) ⇌ H₂CO₃(aq) + OH⁻(aq)

Water, HSO₄⁻, H₂PO₄⁻, and amino acids can also be amphiprotic.

水、HSO₄⁻、H₂PO₄⁻以及氨基酸也是两性物质。

7. Lewis Theory | 7. 路易斯理论

Gilbert Lewis proposed an even broader theory: a Lewis acid is an electron-pair acceptor, and a Lewis base is an electron-pair donor.

吉尔伯特·路易斯提出了更广泛的理论：路易斯酸是电子对接受体，路易斯碱是电子对给予体。

This definition includes reactions with no proton transfer. For example, boron trifluoride reacts with ammonia:

该定义包含了没有质子转移的反应。例如，三氟化硼与氨的反应：

BF₃(g) + NH₃(g) → F₃B–NH₃(s)

BF₃ has an incomplete octet and accepts a lone pair from NH₃, so BF₃ is a Lewis acid and NH₃ is a Lewis base.

BF₃具有不完全的八隅体，接受NH₃的孤对电子，因此BF₃是路易斯酸，NH₃是路易斯碱。

All Brønsted–Lowry acids are also Lewis acids because donating a proton involves accepting an electron pair from the base.

所有布仑斯特-劳里酸同时也是路易斯酸，因为给出质子意味着接受来自碱的电子对。

8. Lewis Theory and Complex Ions | 8. 路易斯理论与配合离子

The Lewis definition is especially useful for transition-metal complex ions. A central metal cation acts as a Lewis acid, while ligands act as Lewis bases because they donate lone pairs.

路易斯定义尤其适用于过渡金属配合离子。中心金属阳离子作为路易斯酸，配体因提供孤对电子而作为路易斯碱。

Cu²⁺(aq) + 4NH₃(aq) ⇌ [Cu(NH₃)₄]²⁺(aq)

Similarly, Fe³⁺ accepts six lone pairs from water or cyanide ions to form hydrated or cyano complexes.

类似地，Fe³⁺接受来自水或氰离子的六对孤对电子，形成水合或氰配合物。

Lewis acids often include metal ions, BF₃, AlCl₃, and SO₃.

路易斯酸常包括金属离子、BF₃、AlCl₃和SO₃。
Lewis bases include NH₃, H₂O, OH⁻, and halide ions.

路易斯碱包括NH₃、H₂O、OH⁻和卤离子。
Coordinate covalent bonds formed this way are central to complex ion chemistry.

由此形成的配位共价键是配合离子化学的核心。

9. Comparison of the Three Theories | 9. 三种理论比较

The table below summarises the key differences.

下表总结了关键区别。

Theory	Acid	Base	Solvent restriction
Arrhenius	Produces H⁺ in water	Produces OH⁻ in water	Aqueous only
Brønsted–Lowry	Proton donor	Proton acceptor	Any medium with proton transfer
Lewis	Electron-pair acceptor	Electron-pair donor	None; includes gas, solid, and solution

Example classification of the same species under each theory:

同一物种在不同理论下的分类示例：

HCl: Arrhenius acid, Brønsted–Lowry acid, Lewis acid.

HCl：阿伦尼乌斯酸、布仑斯特-劳里酸、路易斯酸。
NaOH: Arrhenius base; OH⁻ is a Brønsted–Lowry base and a Lewis base.

NaOH：阿伦尼乌斯碱；OH⁻是布仑斯特-劳里碱和路易斯碱。
BF₃: Not an Arrhenius or Brønsted–Lowry acid (in the classical sense), but a Lewis acid.

BF₃：不是阿伦尼乌斯酸，也不是经典意义上的布仑斯特-劳里酸，但是路易斯酸。

10. Choosing the Right Theory in IB Exams | 10. IB考试中如何选择正确理论

In IB Chemistry multiple-choice and short-answer questions often ask you to identify conjugate pairs or classify a reaction using a specific theory.

在IB化学选择题和简答题中，常要求你识别共轭对，或使用特定理论对反应进行分类。

When the question mentions ‘proton donor/acceptor’, you must apply the Brønsted–Lowry definition. When it mentions ‘electron-pair donor/acceptor’, use Lewis theory.

当题目提到“质子给予体/接受体”时，必须使用布仑斯特-劳里定义；当提到“电子对给予体/接受体”时，使用路易斯理论。

For acid–base equilibria and pH calculations, Brønsted–Lowry theory is the default. For complex-ion formation and non-proton transfer reactions, Lewis theory is necessary.

对于酸碱平衡和pH计算，布仑斯特-劳里理论是默认选择。对于配合离子形成和无质子转移的反应，路易斯理论是必需的。

A common exam trap is calling NH₃ a base because it ‘produces OH⁻’ — better to say it accepts a proton from water, producing OH⁻ as a result.

一个常见考试陷阱是将NH₃称为“产生OH⁻的碱”——更准确的说法是它从水分子获得质子，从而生成OH⁻。

11. Relationship Between the Theories | 11. 三种理论之间的联系

Arrhenius theory is a subset of Brønsted–Lowry theory, which in turn is a subset of Lewis theory.

阿伦尼乌斯理论是布仑斯特-劳里理论的子集，而布仑斯特-劳里理论又是路易斯理论的子集。

Every Arrhenius acid is a Brønsted–Lowry acid, and every Brønsted–Lowry acid is a Lewis acid. The reverse is not true.

所有阿伦尼乌斯酸都是布仑斯特-劳里酸，所有布仑斯特-劳里酸都是路易斯酸；反之则不然。

For example, H⁺ is both a proton and an empty orbital capable of accepting an electron pair, so it fits all three definitions. BF₃ has no protons, so it only fits the Lewis definition.

例如，H⁺既是质子，又具有能接受电子对的空轨道，因此符合全部三种定义。BF₃没有质子，因此只符合路易斯定义。

Arrhenius ⊂ Brønsted–Lowry ⊂ Lewis

This hierarchy helps explain why Lewis theory is the most powerful, yet also the least intuitive for simple aqueous acid–base reactions.

这一层次关系有助于理解为何路易斯理论最强大，但对简单的溶液酸碱反应却最不直观。

12. Key Takeaways for Your Revision | 12. 复习要点总结

You should be able to define and compare the three theories with examples and limitations.

你应该能够定义三种理论，并举例说明它们的异同与局限。

Arrhenius: aqueous H⁺ / OH⁻; limited to water.

阿伦尼乌斯：水溶液中的H⁺/OH⁻；局限在水溶液。
Brønsted–Lowry: proton transfer; works in any solvent.

布仑斯特-劳里：质子转移；适用于任何溶剂。
Lewis: electron-pair transfer; broadest definition, covers complex ions and gas-phase reactions.

路易斯：电子对转移；定义最广，涵盖配合离子和气相反应。
Always identify conjugate acid–base pairs in equilibria.

在平衡问题中始终识别共轭酸碱对。
Use the theory that matches the question’s language: ‘proton’ → Brønsted–Lowry; ‘electron pair’ → Lewis.

选择与题目语言匹配的理论：出现“质子”用布仑斯特-劳里；出现“电子对”用路易斯。

Mastering these distinctions will help you solve IB questions confidently and avoid common misconceptions.

掌握这些区别将帮助你自信地解决IB题目，并避免常见误解。

Published by TutorHao | Chemistry Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

IB Chemistry: Comparison of Major Acid-Base Theories | IB化学：酸碱理论主要学说比较