Year 10 WJEC Chemistry: Formula and Theorem Quick Reference Handbook | Year 10 WJEC 化学：公式定理速查手册

📚 Year 10 WJEC Chemistry: Formula and Theorem Quick Reference Handbook | Year 10 WJEC 化学：公式定理速查手册

This quick reference handbook gathers the key formulas, equations and principles you need to master for the Year 10 WJEC Chemistry course. Use it alongside your class notes and revision materials to strengthen your problem‐solving skills and conceptual understanding.

本速查手册汇集了 Year 10 WJEC 化学课程中必须掌握的核心公式、方程式和原理。结合课堂笔记与复习资料使用，可帮助提升解题能力与概念理解。

1. Atomic Structure and Relative Atomic Mass | 原子结构与相对原子质量

All atoms contain protons, neutrons and electrons. The atomic number (Z) is the number of protons, which defines the element. The mass number (A) is the sum of protons and neutrons: A = Z + N, where N is the number of neutrons. Atoms are electrically neutral, so Z also equals the number of electrons.

所有原子都由质子、中子和电子构成。原子序数 (Z) 是质子数，决定了元素的种类。质量数 (A) 为质子数与中子数之和：A = Z + N，其中 N 为中子数。原子不带电，因此 Z 也等于电子数。

A = Z + N

Relative atomic mass (Ar) is calculated from the masses and abundances of an element’s isotopes. For example, chlorine has two main isotopes. If 75% of atoms have mass 35 and 25% have mass 37, then Ar(Cl) = (75 × 35 + 25 × 37) ÷ 100.

相对原子质量 (Ar) 由同位素的质量和丰度计算得出。例如氯有两种主要同位素，若 75% 的原子质量为 35，25% 为 37，则 Ar(Cl) = (75 × 35 + 25 × 37) ÷ 100。

Ar = Σ (abundance × isotope mass) ÷ 100

Relative molecular mass (Mr) is the sum of the Ar values of all atoms in a chemical formula. For H₂O, Mr = (2 × 1) + 16 = 18.

相对分子质量 (Mr) 是化学式中所有原子 Ar 值的总和。对于 H₂O，Mr = (2 × 1) + 16 = 18。

2. Mole and Molar Mass | 摩尔与摩尔质量

The mole is the SI unit for amount of substance. One mole contains 6.02 × 10²³ particles. The molar mass (M) of a substance is the mass of one mole, with units of g mol⁻¹. It is numerically equal to the relative atomic mass or relative molecular mass.

摩尔是物质的量的国际单位。1 摩尔含有 6.02 × 10²³ 个粒子。物质的摩尔质量 (M) 是 1 摩尔物质的质量，单位为 g mol⁻¹，数值上等于相对原子质量或相对分子质量。

n = m ÷ M

where n is amount in mol, m is mass in g, and M is molar mass in g mol⁻¹. You can rearrange this to m = n × M or M = m ÷ n.

其中 n 为物质的量 (mol)，m 为质量 (g)，M 为摩尔质量 (g mol⁻¹)。该式可变形为 m = n × M 或 M = m ÷ n。

When working with solutions, you often use n = cV (see Section 5). When dealing with gases, n = V (dm³) ÷ 24 at room temperature and pressure (see Section 6).

处理溶液时常用 n = cV（见第 5 节）；处理气体时，在室温和常压下 n = V (dm³) ÷ 24（见第 6 节）。

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