📚 IGCSE Edexcel Chemistry: Formula Summary Handbook | IGCSE Edexcel 化学：公式汇总手册
This handbook brings together the essential formulas you need for IGCSE Edexcel Chemistry. It covers quantitative chemistry, energetics, rates, and more. Master these equations and you will be well-prepared for calculation questions across the syllabus.
本手册汇总了 IGCSE Edexcel 化学所需的关键公式，涵盖定量化学、能量变化、反应速率等主题。熟练掌握这些方程式，你将从容应对课程中各类计算题。
1. Moles, Mass and Molar Mass | 摩尔、质量与摩尔质量
The central relationship in quantitative chemistry is n = m / M, where n is the amount of substance in moles (mol), m is the mass in grams (g), and M is the molar mass in grams per mole (g/mol). It can be rearranged to m = n × M or M = m / n.
定量化学的核心关系为 n = m / M，其中 n 为物质的量(摩尔，mol)，m 为质量(克，g)，M 为摩尔质量(克/摩尔，g/mol)。可变形为 m = n × M 或 M = m / n。
Always ensure your units are consistent: mass in grams, molar mass in g/mol. The molar mass is numerically equal to the relative atomic mass (Ar) or relative formula mass (Mr).
务必确保单位一致：质量用克，摩尔质量用 g/mol。摩尔质量的数值等于相对原子质量 (Ar) 或相对式量 (Mr)。
2. Molar Gas Volume at RTP | 常温常压下气体摩尔体积
At room temperature and pressure (RTP, 25 °C and 1 atm), one mole of any gas occupies a volume of 24 dm³. Therefore, n = V / 24 and V = n × 24, where V is the volume of the gas in dm³.
在常温常压下（RTP，25 °C 和 1 atm），任何气体 1 摩尔的体积为 24 dm³。因此，n = V / 24 和 V = n × 24，其中 V 为气体体积(dm³)。
If the volume is given in cm³, first convert to dm³ by dividing by 1000 (1 dm³ = 1000 cm³). This simple conversion is vital for correct mole calculations involving gases.
若体积以 cm³ 给出，需先除以 1000 转换为 dm³（1 dm³ = 1000 cm³）。该转换对于涉及气体的摩尔计算至关重要。
3. Solutions and Concentration | 溶液与浓度
The concentration of a solution in mol/dm³ is given by c = n / V, where n is the number of moles of solute and V is the volume of solution in dm³. Rearranged forms are n = c × V and V = n / c.
溶液的摩尔浓度（mol/dm³）由 c = n / V 给出，其中 n 为溶质的摩尔数，V 为溶液的体积(dm³)。变形式为 n = c × V 和 V = n / c。
Concentration can also be expressed in g/dm³: concentration (g/dm³) = mass (g) / volume (dm³). You can convert between the two using molar mass: concentration (mol/dm³) = concentration (g/dm³) / M.
浓度也可用 g/dm³ 表示：浓度 (g/dm³) = 质量 (g) / 体积 (dm³)。可通过摩尔质量相互转换：浓度 (mol/dm³) = 浓度 (g/dm³) / M。
4. Dilution of Solutions | 溶液稀释
When a solution is diluted by adding more solvent, the number of moles of solute stays the same. The dilution formula is c₁V₁ = c₂V₂, where c₁ and V₁ are the initial concentration and volume, and c₂ and V₂ are the concentration and volume after dilution.
当加入溶剂稀释溶液时，溶质的摩尔数保持不变。稀释公式为 c₁V₁ = c₂V₂，其中 c₁ 和 V₁ 为初始浓度和体积，c₂ 和 V₂ 为稀释后的浓度和体积。
Both volumes must be in the same unit (usually dm³ or cm³) and both concentrations in the same unit. This relationship is widely used in preparing standard solutions and in titration contexts.
两个体积需用相同单位（通常为 dm³ 或 cm³），两个浓度也需用相同单位。该关系广泛用于配制标准溶液和滴定中。
5. Percentage Yield and Atom Economy | 产率与原子经济性
The percentage yield evaluates the efficiency of a reaction in producing the desired product: % yield = (actual yield / theoretical yield) × 100%. Theoretical yield is calculated from the limiting reactant using mole ratios.
产率用于评价反应生成目标产物的效率：产率 = (实际产量 / 理论产量) × 100%。理论产量由限量反应物根据摩尔比计算得出。
Atom economy measures how much of the starting materials ends up in the useful product: atom economy = (Mr of desired product / sum of Mr of all reactants) × 100%. A higher atom economy indicates a more sustainable process with less waste.
原子经济性衡量起始原料有多少最终进入目标产物：原子经济性 = (目标产物 Mr / 所有反应物 Mr 之和) × 100%。原子经济性越高，过程越绿色，废物越少。
6. Energy Changes: Calorimetry | 能量变化：量热法
The heat energy transferred in a reaction is measured using Q = m c ΔT, where m is the mass of the substance heated (often the solution, in g), c is the specific heat capacity (for water, 4.18 J/g°C), and ΔT is the temperature change (°C).
反应中传递的热量通过 Q = m c ΔT 测量，其中 m 为被加热物质的质量（通常为溶液，g），c 为比热容（水为 4.18 J/g°C），ΔT 为温度变化 (°C)。
To calculate the molar enthalpy change: ΔH = −Q / n (in J/mol or kJ/mol). Here, n is the number of moles of the limiting reactant that reacted. The negative sign ensures that exothermic reactions give a negative ΔH.
计算摩尔焓变：ΔH = −Q / n（单位 J/mol 或 kJ/mol）。n 为参与反应的限量反应物的摩尔数。负号确保放热反应 ΔH 为负值。
If Q is in joules, convert to kJ by dividing by 1000 when quoting ΔH in kJ/mol. Always specify the reaction and the amount of reactant.
若 Q 以焦耳为单位，当 ΔH 以 kJ/mol 表示时需除以 1000。必须指明反应及反应物的量。
7. Rate of Reaction | 反应速率
The mean rate of a reaction is calculated as the change in the amount of a reactant or product divided by the time taken: rate = Δ(quantity) / time. The quantity can be mass (g), volume of gas evolved (cm³), or concentration.
平均反应速率由反应物或产物量的变化除以时间得到：速率 = Δ(量) / 时间。该量可以是质量(g)、产生气体的体积(cm³)或浓度。
Common units include g/s, cm³/s, and mol/dm³·s. For a graph of product formed against time, the rate at a particular instant is given by the gradient of the tangent.
常见单位有 g/s、cm³/s、mol/dm³·s。在产物-时间坐标图上，某时刻的瞬时速率由该点切线的斜率求得。
8. Relative Atomic Mass from Isotopic Abundances | 同位素丰度计算相对原子质量
The relative atomic mass (Ar) of an element is the weighted average mass of its isotopes relative to 1/12th of a carbon-12 atom. It is calculated using: Ar = [(% abundance₁ × mass number₁) + (% abundance₂ × mass number₂) + …] / 100.
元素的相对原子质量 (Ar) 是其同位素相对质量对碳-12 原子 1/12 的加权平均。计算式：Ar = [(丰度%₁ × 质量数₁) + (丰度%₂ × 质量数₂) + …] / 100。
If the abundances are given as decimals (fractions of 1), then simply sum the products: Ar = Σ (fraction × mass number). Always check the total abundance adds up to 100% or 1.
若丰度以小数形式给出（分数 1），则直接求和：Ar = Σ (分数 × 质量数)。务必检查总丰度是否为 100% 或 1。
9. Empirical and Molecular Formulae | 经验式与分子式
The empirical formula gives the simplest whole-number ratio of atoms in a compound. It is found by converting the mass or percentage of each element to moles (n = m / M), then dividing each mole value by the smallest to get the ratio.
经验式表示化合物中各原子最简整数比。通过将各元素的质量或百分比转换为摩尔（n = m / M），再将各摩尔值除以其中的最小值得到比。
To obtain the molecular formula, you need the Mr of the compound. First find the empirical formula mass, then calculate n = Mr(molecular) / Mr(empirical). Multiply the subscripts in the empirical formula by this integer n.
为得到分子式，需要化合物的 Mr。先求出经验式量，再计算 n = Mr(分子) / Mr(经验式)。将经验式中各下标乘以该整数 n 即得分子式。
10. Titration Calculations | 滴定计算
In a titration, the unknown concentration of an acid or alkali is determined using a standard solution. The formula n = c × V (with V in dm³) gives the moles of the known reactant, and the mole ratio from the balanced equation is then applied.
在滴定中，用标准溶液测定未知酸液或碱液的浓度。利用 n = c × V（V 以 dm³ 计）算出已知反应物的摩尔数，再结合配平方程中的摩尔比推算出未知量。
For the reaction aA + bB → products, the relationship is: (cAVA) / a = (cBVB) / b. This formula directly links the volumes and concentrations of the two solutions. Always convert cm³ to dm³ by dividing by 1000.
对于反应 aA + bB → 产物，存在关系：(cAVA) / a = (cBVB) / b。此式直接建立两种溶液的体积和浓度的联系。务必先将 cm³ 除以 1000 换算为 dm³。
Pay attention to the stoichiometric coefficients when the reacting ratio is not 1:1; incorrect mole ratios are a common source of error in titration calculations.
当反应比例不是 1:1 时，务必注意化学计量系数；错误的摩尔比是滴定计算中常见的出错原因。
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