Displacement Reactions | 置换反应

📚 Displacement Reactions | 置换反应

Displacement reactions are one of the most important reaction types in the KS3 CIE chemistry syllabus. They show how a more reactive element can take the place of a less reactive element from a compound. Once you know the reactivity series, you can predict whether a displacement will happen and what the products will be.

置换反应是 KS3 CIE 化学大纲中最重要的反应类型之一。它展示了一种较活泼的元素如何从化合物中取代较不活泼的元素。一旦你掌握了金属活动性顺序，就可以预测置换反应是否会发生以及生成什么产物。

1. What Is a Displacement Reaction? | 什么是置换反应？

A displacement reaction occurs when one element pushes another element out of its compound. The more reactive element takes the place of the less reactive element and forms a new compound.

置换反应是指一种元素将另一种元素从其化合物中取代出来。较活泼的元素占据了较不活泼元素的位置，并形成新的化合物。

→ AC + B. Element A is more reactive than element B, so it replaces B in the compound BC.

一般模式可写成：A + BC → AC + B。元素 A 比元素 B 更活泼，因此它取代了化合物 BC 中的 B。

For example, when iron is added to copper(II) sulfate solution, iron takes copper's place: iron + copper(II) sulfate → iron(II) sulfate + copper.

例如，将铁加入硫酸铜溶液中时，铁取代了铜的位置：铁 + 硫酸铜 → 硫酸亚铁 + 铜。

Fe + CuSO₄ → FeSO₄ + Cu

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2. The Reactivity Series | 金属活动性顺序

The reactivity series lists metals from the most reactive to the least reactive. A metal higher in the series can displace a metal lower in the series from a compound.

金属活动性顺序将金属按从最活泼到最不活泼的顺序排列。顺序中位置较高的金属可以从化合物中置换出位置较低的金属。

For the KS3 CIE course, you need to remember this order, including the two reference non-metals carbon and hydrogen.

在 KS3 CIE 课程中，你需要记住这个顺序，包括两个作为参考点的非金属：碳和氢。

Position	Element	Symbol	Reactivity
1	Potassium	K	Most reactive
2	Sodium	Na	↓
3	Calcium	Ca	↓
4	Magnesium	Mg	↓
5	Aluminium	Al	↓
6	Carbon	C	Non-metal reference
7	Zinc	Zn	↓
8	Iron	Fe	↓
9	Lead	Pb	↓
10	Hydrogen	H	Non-metal reference
11	Copper	Cu	↓
12	Silver	Ag	↓
13	Gold	Au	Least reactive

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3. Metals Displacing Metals from Solutions | 金属从盐溶液中置换金属

When a more reactive metal is placed in a solution of a less reactive metal salt, the more reactive metal gives away electrons and enters the solution as ions. The less reactive metal ion gains the electrons and forms solid metal.

当较活泼的金属放入较不活泼金属的盐溶液中时，较活泼金属失去电子并作为离子进入溶液。较不活泼的金属离子获得电子，形成固态金属。

A classic example is zinc added to blue copper(II) sulfate solution.

一个典型例子是将锌加入蓝色的硫酸铜溶液中。

Zn + CuSO₄ → ZnSO₄ + Cu

Zinc is more reactive than copper, so zinc displaces copper. The blue colour of the solution fades because copper ions are removed, and a pink-brown deposit of copper metal forms on the zinc.

锌比铜更活泼，因此锌置换出铜。溶液的蓝色逐渐褪去，因为铜离子被去除，同时在锌表面形成粉棕色铜金属沉积。

um added to zinc chloride solution: magnesium + zinc chloride → magnesium chloride + zinc.

另一个例子是将镁加入氯化锌溶液中：镁 + 氯化锌 → 氯化镁 + 锌。

If copper is added to zinc sulfate solution, no reaction occurs because copper is less reactive than zinc.

如果将铜加入硫酸锌溶液中，则不会发生反应，因为铜不如锌活泼。

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4. Metals Displacing Hydrogen from Acids | 金属从酸中置换氢气

Acids contain hydrogen. When a reactive metal is added to an acid, the metal can displace hydrogen from the acid, producing a salt and hydrogen gas.

酸中含有氢。当活泼金属加入酸中时，金属可以从酸中置换出氢，生成盐和氢气。

The general word equation is: metal + acid → salt + hydrogen.

一般文字表达式为：金属 + 酸 → 盐 + 氢气。

cts with hydrochloric acid: magnesium + hydrochloric acid → magnesium chloride + hydrogen.

例如，镁与盐酸反应：镁 + 盐酸 → 氯化镁 + 氢气。

Mg + 2HCl → MgCl₂ + H₂

Hydrogen gas can be tested using a lit splint. If hydrogen is present, it burns with a characteristic squeaky pop sound.

氢气可以用点燃的木条检验。如果存在氢气，它会燃烧并发出特有的爆鸣声（squeaky pop）。

Metals above hydrogen in the reactivity series can displace hydrogen from acids. Metals below hydrogen, such as copper, silver and gold, do not react with dilute acids in this way.

活动性顺序中位于氢之前的金属可以从酸中置换出氢。位于氢之后的金属，如铜、银和金，不会以这种方式与稀酸反应。

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5. The Thermite Reaction: A Special Metal Displacement | 铝热反应：特殊的金属置换

Aluminium is more reactive than iron, so aluminium can displace iron from iron(III) oxide. This reaction is called the thermite reaction.

铝比铁更活泼，因此铝可以从氧化铁中置换出铁。这个反应称为铝热反应。

The thermite reaction is: aluminium + iron(III) oxide → aluminium oxide + iron.

铝热反应为：铝 + 氧化铁 → 氧化铝 + 铁。

2Al + Fe₂O₃ → Al₂O₃ + 2Fe

The thermite reaction is highly exothermic, meaning it releases a large amount of heat. It is so hot that the iron produced is molten and may glow orange or white.

铝热反应是高度放热的，也就是说它会释放大量热量。反应温度极高，生成的铁呈熔融状态，可能发出橙色或白色光芒。

This reaction is used in some railway welding processes because the molten iron can fill gaps between rails.

该反应用于某些铁路焊接工艺中，因为熔融的铁可以填充钢轨之间的缝隙。

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6. Halogen Displacement Reactions | 卤素置换反应

Displacement does not only happen with metals. Halogens, which are Group 7 elements, can

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