Acids, Bases and Salts | 酸、碱和盐

📚 Acids, Bases and Salts | 酸、碱和盐

Understanding acids, bases and salts is fundamental to chemistry. In Edexcel IGCSE Science, this topic explains how these substances interact, how we measure acidity using the pH scale, and how salts are formed through neutralisation reactions. Mastering these concepts will help you excel in both theoretical questions and practical investigations.

理解酸、碱和盐是化学的基础。在爱德思IGCSE科学课程中，这一主题阐释了这些物质如何相互作用，我们如何使用pH标度测量酸碱度，以及盐是如何通过中和反应形成的。掌握这些概念将帮助你在理论题和实验考查中都取得优异成绩。

1. What are Acids and Bases? | 什么是酸和碱？

Acids are substances that release hydrogen ions (H⁺) when dissolved in water. They have a sour taste and can turn blue litmus paper red. Bases are substances that can neutralise acids to produce a salt and water. Soluble bases are called alkalis; they release hydroxide ions (OH⁻) in water and turn red litmus paper blue. Importantly, bases include metal oxides, metal hydroxides and metal carbonates.

酸是在水中溶解时释放氢离子（H⁺）的物质。它们有酸味，能使蓝色石蕊试纸变红。碱是能中和酸生成盐和水的物质。可溶性的碱称为碱溶液；它们在水里释放氢氧根离子（OH⁻），使红色石蕊试纸变蓝。重要的是，碱包括金属氧化物、金属氢氧化物和金属碳酸盐。

2. The pH Scale and Indicators | pH标度和指示剂

The pH scale measures how acidic or alkaline a solution is. It ranges from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral. Indicators are dyes that change colour depending on pH. Universal indicator gives a full range of colours, while litmus only shows acid or alkali.

pH标度用于衡量溶液酸碱性的强弱。其范围从0（强酸性）到14（强碱性），7为中性。指示剂是随pH变化而改变颜色的染料。通用指示剂呈现整个颜色范围，而石蕊只区分酸和碱。

Universal indicator colours: red (pH 1-3), orange (4-5), yellow (6), green (7), blue (8-11), purple (12-14).

通用指示剂颜色：红（pH 1-3）、橙（4-5）、黄（6）、绿（7）、蓝（8-11）、紫（12-14）。

3. Common Acids and Alkalis | 常见的酸和碱

In the laboratory, we frequently use hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Common alkalis include sodium hydroxide (NaOH), potassium hydroxide (KOH) and calcium hydroxide (Ca(OH)₂). Household ammonia solution is also weakly alkaline.

实验室中经常使用盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。常见的碱性溶液包括氢氧化钠（NaOH）、氢氧化钾（KOH）和氢氧化钙（Ca(OH)₂）。家用的氨水也呈弱碱性。

4. Reactions of Acids with Metals | 酸与金属的反应

Acids react with certain metals to produce a salt and hydrogen gas. The general equation is:

acid + metal → salt + hydrogen

For example, zinc reacts with hydrochloric acid: Zn + 2HCl → ZnCl₂ + H₂. The test for hydrogen gas is a ‘squeaky pop’ with a lighted splint.

酸与某些金属反应生成盐和氢气。通式为：酸 + 金属 → 盐 + 氢气。例如，锌与盐酸反应：Zn + 2HCl → ZnCl₂ + H₂。检验氢气的方法是用点燃的木条靠近集气口，会听到”噗”的一声。

5. Reactions of Acids with Metal Oxides and Hydroxides | 酸与金属氧化物和氢氧化物的反应

Metal oxides and hydroxides are bases. They neutralise acids to form a salt and water only. The word equations are:

acid + metal oxide → salt + water
acid + metal hydroxide → salt + water

For instance, copper(II) oxide + sulfuric acid → copper(II) sulfate + water: CuO + H₂SO₄ → CuSO₄ + H₂O. Sodium hydroxide with hydrochloric acid: NaOH + HCl → NaCl + H₂O.

金属氧化物和氢氧化物是碱。它们与酸中和只生成盐和水。例如，氧化铜与硫酸反应：CuO + H₂SO₄ → CuSO₄ + H₂O。氢氧化钠与盐酸：NaOH + HCl → NaCl + H₂O。

6. Reactions of Acids with Metal Carbonates | 酸与金属碳酸盐的反应

Metal carbonates are also bases. When they react with acids, they produce a salt, water and carbon dioxide gas. The general

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