📚 Making Salts - Acids and Carbonates | 用酸和碳酸盐制盐
In KS3 chemistry, making salts is one of the most important practical skills. When an acid reacts with a carbonate, the products are always a salt, water and carbon dioxide. This reaction is useful because the fizzing shows a gas is being produced, and the salt can then be collected by filtration and crystallisation.
在KS3化学中，制盐是最重要的实验技能之一。当酸与碳酸盐反应时，产物总是盐、水和二氧化碳。这个反应非常有用，因为冒泡的现象表明正在产生气体，随后可以通过过滤和结晶来收集盐。
1. What Is a Salt? | 什么是盐？
A salt is an ionic compound formed when the hydrogen ions in an acid are replaced by metal ions or ammonium ions. Salts are not just table salt; they include many useful compounds such as copper sulfate, calcium chloride and potassium nitrate. In the laboratory, salts can be made by reacting acids with metals, bases or carbonates.
盐是一种离子化合物，当酸中的氢离子被金属离子或铵根离子取代时形成。盐不只是食盐，还包括许多有用的化合物，例如硫酸铜、氯化钙和硝酸钾。在实验室中，盐可以通过酸与金属、碱或碳酸盐反应来制取。
Common salts you may meet in KS3 include sodium chloride, copper sulfate, magnesium sulfate and calcium carbonate. Each salt has a name that tells you which acid and which metal were used to make it.
你在KS3阶段可能会遇到的常见盐包括氯化钠、硫酸铜、硫酸镁和碳酸钙。每种盐的名称都能告诉你它是用哪种酸和哪种金属制得的。
2. Acids and Carbonates: The Key Reaction | 酸与碳酸盐：关键反应
Carbonates are compounds that contain the carbonate ion, CO₃²⁻. When a carbonate reacts with an acid, the general word equation is always the same:
碳酸盐是含有碳酸根离子 CO₃²⁻ 的化合物。当碳酸盐与酸反应时，通用的文字方程式总是相同的：
acid + carbonate → salt + water + carbon dioxide
酸 + 碳酸盐 → 盐 + 水 + 二氧化碳
This is an example of a neutralisation reaction because the acid is used up. Effervescence, or fizzing, is observed because carbon dioxide gas is released rapidly from the reaction mixture.
这是一个中和反应的例子，因为酸被反应掉了。由于二氧化碳气体从反应混合物中迅速释放，可以观察到冒泡或起泡的现象。
3. Naming the Salt | 盐的命名
The name of a salt has two parts. The first part comes from the metal in the carbonate, and the second part comes from the acid. For example, copper carbonate reacting with sulfuric acid makes copper sulfate.
盐的名称由两部分组成。第一部分来自碳酸盐中的金属，第二部分来自酸。例如，碳酸铜与硫酸反应生成硫酸铜。
| Acid | Salt name ending | Example |
|---|---|---|
| Hydrochloric acid | -chloride | copper chloride |
| Sulfuric acid | -sulfate | copper sulfate |
| Nitric acid | -nitrate | copper nitrate |
中文表格：酸、盐名称后缀和示例。盐酸生成氯化物，例如氯化铜；硫酸生成硫酸盐，例如硫酸铜；硝酸生成硝酸盐，例如硝酸铜。
Always check both parts of the name: the metal part does not change when the carbonate reacts, but the acid part changes to the correct ending.
一定要检查名称的两个部分：碳酸盐反应时金属部分不变，但酸的部分会变成正确的后缀。
4. Balanced Symbol Equations | 配平的符号方程式
Writing symbol equations helps show the atoms involved in the reaction. One example is calcium carbonate reacting with hydrochloric acid:
书写符号方程式有助于展示反应中涉及的原子。一个例子是碳酸钙与盐酸反应：
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
碳酸钙 + 盐酸 → 氯化钙 + 水 + 二氧化碳
One calcium atom, one carbon atom and three oxygen atoms from the carbonate appear in the products as calcium chloride, water and carbon dioxide. The equation is balanced because the same number of each type of atom appears on both sides.
来自碳酸盐的一个钙原子、一个碳原子和三个氧原子在生成物中分别出现在氯化钙、水和二氧化碳中。该方程式已经配平，因为每种原子的数量在反应前后相等。
Another common example is magnesium carbonate reacting with sulfuric acid:
另一个常见的例子是碳酸镁与硫酸反应：
MgCO₃ + H₂SO₄ → MgSO₄ + H₂O + CO₂
碳酸镁 + 硫酸 → 硫酸镁 + 水 + 二氧化碳
Notice that in each carbonate reaction, one molecule of carbonate produces exactly one molecule of carbon dioxide and one molecule of water.
请注意，在每个碳酸盐反应中，一个碳酸盐分子恰好生成一个二氧化碳分子和一个水分子。
5. Practical: Making Copper Sulfate from Copper Carbonate | 实验：由碳酸铜制取硫酸铜
To make copper sulfate crystals, add black copper carbonate powder to warm dilute sulfuric acid. Stir the mixture until the fizzing stops, showing that all the acid has reacted. The mixture may still contain unreacted copper carbonate, so filter it to remove the excess solid. Then evaporate the blue solution gently to obtain blue copper sulfate crystals.
要制取硫酸铜晶体，将黑色的碳酸铜粉末加入温热的稀硫酸中。搅拌混合物直到不再冒泡，这表明所有酸都已反应。混合物中仍可能含有未反应的碳酸铜，因此需要过滤除去过量的固体。然后缓慢蒸发蓝色溶液，得到蓝色的硫酸铜晶体。
- Add copper carbonate to sulfuric acid a little at a time.
- Stir until no more bubbles form.
- Filter the mixture to remove excess copper carbonate.
- Evaporate the filtrate slowly to form crystals.
中文步骤：每次少量地将碳酸铜加入硫酸中；搅拌直到不再有气泡生成；过滤混合物以除去过量的碳酸铜；缓慢蒸发滤液以形成晶体。
This method works because copper carbonate is insoluble in water, so the excess solid can be removed easily by filtration. The blue colour of the solution comes from copper ions.
这种方法之所以有效，是因为碳酸铜不溶于水，因此多余的固体可以通过过滤轻松除去。溶液的蓝色来自铜离子。
6. Observing the Reaction | 观察反应
When an acid reacts with a carbonate, you will usually see effervescence as carbon dioxide gas escapes. If enough acid is present, the solid carbonate disappears and a clear solution remains. The solution may change colour depending on the salt made. For example, copper carbonate with sulfuric acid gives a blue solution.
当酸与碳酸盐反应时，通常会看到二氧化碳气体逸出产生起泡现象。如果有足够的酸，固体碳酸盐会消失，留下澄清的溶液。溶液的颜色可能因生成的盐不同而变化。例如，碳酸铜与硫酸反应会得到蓝色溶液。
The temperature of the mixture may rise slightly because neutralisation reactions are often exothermic. However, the most obvious sign is the rapid release of gas bubbles.
混合物的温度可能会略微升高，因为中和反应通常是放热的。然而，最明显的迹象是气体气泡的快速释放。
If the fizzing stops while some solid carbonate remains, it means the acid has been used up. You can add more acid or filter the mixture to remove the leftover carbonate.
如果不再冒泡但仍有固体碳酸盐剩余，说明酸已经被耗尽。你可以加入更多的酸，或者过滤混合物以除去剩余的碳酸盐。
7. Testing for Carbon Dioxide Gas | 二氧化碳气体的检验
Carbon dioxide can be identified using limewater. Bubble the gas through limewater; if carbon dioxide is present, the limewater turns milky or cloudy. This happens because insoluble calcium carbonate forms in the limewater.
二氧化碳可以用石灰水来检验。将气体通入石灰水中；如果存在二氧化碳，石灰水会变浑浊或呈乳白色。这是因为石灰水中生成了不溶性的碳酸钙。
CO₂ + Ca(OH)₂ → CaCO₃ + H₂O
二氧化碳 + 氢氧化钙 → 碳酸钙 + 水
Limewater is a solution of calcium hydroxide, Ca(OH)₂. The milky colour is a positive test for carbon dioxide. If the gas is not carbon dioxide, the limewater remains clear.
石灰水是氢氧化钙 Ca(OH)₂ 的溶液。变浑浊是二氧化碳的阳性检验结果。如果气体不是二氧化碳，石灰水会保持澄清。
8. Why Excess Carbonate Is Used | 为什么使用过量碳酸盐
In salt preparation, the carbonate is usually added until no more fizzing occurs. Using excess carbonate guarantees that all the acid has reacted. Since most carbonates are insoluble in water, the unreacted excess can be removed by filtration. This leaves a pure salt solution that can be crystallised.
在制盐时，通常会加入碳酸盐直到不再冒泡。使用过量的碳酸盐能确保所有酸都已反应。由于大多数碳酸盐不溶于水，未反应的过量部分可以通过过滤除去。这样就得到纯净的盐溶液，可以进一步结晶。
If excess acid were used instead, it would be difficult to remove because the acid is soluble in water. That is why adding excess insoluble carbonate is a safer and simpler method for making a pure salt.
如果使用过量的酸，则很难除去，因为酸可溶于水。这就是为什么加入过量的不溶性碳酸盐是制取纯净盐的更安全、更简单的方法。
After filtration, the solid left on the filter paper is called the residue, and the liquid that passes through is called the filtrate.
过滤后，留在滤纸上的固体称为滤渣，通过滤纸的液体称为滤液。
9. Common Carbonates and Their Salts | 常见碳酸盐及其盐
Different carbonates can be used to make different salts. Limestone, marble and chalk are all forms of calcium carbonate. Sodium carbonate is used in washing soda, and copper carbonate is a green or black solid used in school laboratories.
不同的碳酸盐可以制取不同的盐。石灰石、大理石和白垩都是碳酸钙的形式。碳酸钠用于洗涤碱，碳酸铜是学校实验室中使用的绿色或黑色固体。
| Carbonate | Formula | Reaction with acid |
|---|---|---|
| Calcium carbonate | CaCO₃ | calcium chloride + water + CO₂ with HCl |
| Sodium carbonate | Na₂CO₃ | sodium sulfate + water + CO₂ with H₂SO₄ |
| Copper carbonate | CuCO₃ | copper sulfate + water + CO₂ with H₂SO₄ |
| Zinc carbonate | ZnCO₃ | zinc nitrate + water + CO₂ with HNO₃ |
中文表格：碳酸盐、化学式和与酸反应的产物。碳酸钙与盐酸生成氯化钙、水和二氧化碳；碳酸钠与硫酸生成硫酸钠、水和二氧化碳；碳酸铜与硫酸生成硫酸铜、水和二氧化碳；碳酸锌与硝酸生成硝酸锌、水和二氧化碳。
10. Everyday Examples and Applications | 日常实例与应用
Carbonate-acid reactions are common in daily life. Antacid tablets often contain calcium carbonate and neutralise excess stomach acid. Acid rain, which contains sulfuric and nitric acids, can react with limestone buildings and damage them. Baking powder contains sodium hydrogencarbonate, which releases carbon dioxide when mixed with acidic ingredients.
碳酸盐与酸的反应在日常生活中很常见。抗酸药片通常含有碳酸钙，能中和过多的胃酸。含有硫酸和硝酸的酸雨会与石灰岩建筑反应并损坏它们。泡打粉含有碳酸氢钠，与酸性原料混合时释放二氧化碳。
In the kitchen, sodium hydrogencarbonate is used to make cakes rise because the carbon dioxide gas forms bubbles in the mixture. This is another example of the same acid-carbonate chemistry.
在厨房中，碳酸氢钠被用来使蛋糕膨胀，因为二氧化碳气体在面糊中形成气泡。这是酸与碳酸盐化学的又一个应用实例。
11. Key Word Summary | 关键词总结
Learn these key terms and their meanings to help you answer KS3 questions confidently.
记住以下关键术语及其含义，帮助你自信地回答KS3问题。
- Acid: a substance with pH below 7 that donates hydrogen ions.
- Carbonate: a compound containing the CO₃²⁻ ion.
- Salt: an ionic compound formed when acid reacts with a metal, base or carbonate.
- Effervescence: rapid escape of gas bubbles from a liquid.
- Limewater test: a test for carbon dioxide that turns milky.
- Filtration: a method used to separate an insoluble solid from a liquid.
- Crystallisation: the process of forming solid crystals from a solution by evaporation.
中文术语：酸是pH低于7并能提供氢离子的物质；碳酸盐是含有CO₃²⁻离子的化合物；盐是酸与金属、碱或碳酸盐反应生成的离子化合物；冒泡是气体气泡从液体中快速逸出的现象；石灰水检验是使石灰水变浑浊的二氧化碳检验方法；过滤是将不溶性固体从液体中分离的方法；结晶是通过蒸发从溶液中形成固体晶体的过程。
12. Common Mistakes and Exam Tips | 常见错误与考试提示
A common mistake is forgetting that water
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