定义Definition
物质的量是国际单位制的七个基本物理量之一，符号 n，表示含有一定数目基本单元（原子、分子、离子等）的集合体，单位为摩尔（mol）。1 mol 任何物质含有 6.022 140 76 × 10²³ 个基本单元。
Amount of substance is one of the seven base quantities of the SI, symbol n; it measures a collection of a given number of elementary entities (atoms, molecules, ions and so on), and its unit is the mole (mol). One mole of anything contains 6.022 140 76 × 10²³ entities.
与其他量的关系Links to other quantities
物质的量把微观粒子数和宏观可测量的量联系起来：n = N/N_A（粒子数 N，阿伏伽德罗常数 N_A）；n = m/M（质量 m，摩尔质量 M）；气体 n = V/V_m（标准状况下 V_m ≈ 22.4 L mol⁻¹）；溶液 n = cV（物质的量浓度 c，溶液体积 V）。
Amount of substance links particle numbers to measurable quantities: n = N/N_A (number of particles N, Avogadro constant N_A); n = m/M (mass m, molar mass M); for gases n = V/V_m (V_m ≈ 22.4 L mol⁻¹ at 0 °C and 101.325 kPa); for solutions n = cV (molar concentration c, solution volume V).
化学计算的核心The centre of chemical calculations
化学方程式中的系数之比就是参加反应的各物质的物质的量之比。例如 2H₂ + O₂ → 2H₂O 表示 2 mol H₂ 与 1 mol O₂ 反应生成 2 mol H₂O。计算时一般先把已知的质量、体积或浓度换算成物质的量，按系数比求出未知物的物质的量，再换算回所需的量。
The coefficients in a balanced equation give the ratio of amounts of the substances reacting. 2H₂ + O₂ → 2H₂O means 2 mol of H₂ react with 1 mol of O₂ to give 2 mol of H₂O. Calculations usually convert a known mass, volume or concentration into an amount, use the coefficient ratio to find the unknown amount, and convert back to the quantity required.
使用注意Points to watch
使用物质的量时必须指明基本单元，如 1 mol H、1 mol H₂、1 mol H⁺ 是不同的。“物质的量”四个字是一个整体，不能简化为“物质量”，也不应称为“摩尔数”。
The entity must always be specified: 1 mol of H, 1 mol of H₂ and 1 mol of H⁺ are different. The Chinese name 物质的量 is a single term; it should not be shortened to 物质量 or called 摩尔数 (number of moles).
年表Timeline
- 1811
阿伏伽德罗提出同温同压下同体积气体含有相同数目的分子
Avogadro proposes that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules
- 1971
第 14 届国际计量大会把物质的量列为 SI 基本量，单位摩尔
The 14th CGPM adopts amount of substance as an SI base quantity with the mole as unit
- 2019
摩尔改由固定的阿伏伽德罗常数定义
The mole is redefined by a fixed value of the Avogadro constant
相关公式Formulas
例题Worked example
9.0 g 水：n = 9.0/18.0 = 0.50 mol，含 0.50 × 6.02×10²³ = 3.0×10²³ 个分子。
9.0 g of water: n = 9.0/18.0 = 0.50 mol, i.e. 3.0×10²³ molecules.
例题Worked example
1.204×10²⁴ 个 CO₂ 分子是 2.00 mol，含 4.00 mol 氧原子。
1.204×10²⁴ CO₂ molecules = 2.00 mol, containing 4.00 mol of O atoms.