Year 12 Edexcel Chemistry: Formula & Theorem Quick Reference | 12年级 Edexcel 化学：公式定理速查手册

📚 Year 12 Edexcel Chemistry: Formula & Theorem Quick Reference | 12年级 Edexcel 化学：公式定理速查手册

This quick reference compiles the essential formulas, laws, and equations you need for Year 12 Edexcel AS Chemistry. Use it to revise mole calculations, energetics, kinetics, equilibrium, and organic general formulae. Every entry is paired with a concise explanation in English and Chinese to support bilingual learners.

本速查手册汇集了 12 年级 Edexcel AS 化学所需的核心公式、定律与方程式。可用于复习摩尔计算、能量学、动力学、平衡以及有机通式。每个条目均配有中英双语解释，方便双语学习者查阅。

1. Mole and Mass | 摩尔与质量

The mole is the SI unit for amount of substance. One mole of any species contains exactly 6.02 × 10²³ particles (Avogadro constant, L or Nₐ).

摩尔是物质的量的 SI 单位。1 mol 任何物质恰好包含 6.02 × 10²³ 个粒子（阿伏伽德罗常数，L 或 Nₐ）。

The mass of one mole of a substance is its molar mass M, expressed in g mol⁻¹. For atoms, M is numerically equal to the relative atomic mass Aᵣ.

1 mol 物质的质量即其摩尔质量 M，单位为 g mol⁻¹。对原子而言，M 在数值上等于相对原子质量 Aᵣ。

The core equation linking mass, molar mass and moles is:

质量、摩尔质量与摩尔数之间的核心关系式为：

n = m ÷ M

where n is amount in mol, m is mass in g, and M is molar mass in g mol⁻¹. Always convert mass into grams before substituting.

其中 n 为物质的量 (mol)，m 为质量 (g)，M 为摩尔质量 (g mol⁻¹)。代入前务必将质量转换为克。

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2. Molar Volume of Gases | 气体摩尔体积

At room temperature and pressure (RTP: 20 °C and 1 atm), one mole of any gas occupies 24 dm³. This is called the molar gas volume.

在室温和常压下（RTP: 20 °C，1 atm），1 mol 任何气体的体积为 24 dm³。此即气体摩尔体积。

The relation between volume and moles is:

体积与摩尔数的关系为：

V (dm³) = n × 24

or rearranged: n = V (dm³) ÷ 24. If the volume is given in cm³, divide by 1000 first.

或变换为：n = V (dm³) ÷ 24。若体积以 cm³ 给出，需先除以 1000。

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3. Concentration and Titration | 浓度与滴定

Concentration c of a solution is defined as the amount of solute dissolved per unit volume of solution.

溶液的浓度 c 定义为单位体积溶液中溶解的溶质的物质的量。

c = n ÷ V

where c is in mol dm⁻³, n in mol, and V in dm³. When volume is given in cm³, convert to dm³ by dividing by 1000.

其中 c 单位为 mol dm⁻³，n 为 mol，V 为 dm³。若体积单位为 cm³，需除以 1000 转为 dm³。

In a titration involving a reaction aA + bB → products, the mole ratio can be used:

滴定涉及反应 aA + bB → 产物时，可利用摩尔比：

cₐVₐ / a = c_b V_b / b

For 1:1 reactions this simplifies to cₐVₐ = c_bV_b.

对于 1:1 反应，该式简化为 cₐVₐ = c_bV_b。

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4. Ideal Gas Equation | 理想气体方程

The ideal gas equation combines pressure, volume, temperature and moles for a gas behaving ideally:

理想气体方程将理想气体的压强、体积、温度与摩尔数关联：

pV = nRT

p = pressure in Pa; V = volume in m³; n = amount in mol; T = temperature in K; R = gas constant = 8.31 J K⁻¹ mol⁻¹.

p = 压强 (Pa)；V = 体积 (m³)；n = 物质的量 (mol)；T = 热力学温度 (K)；R = 气体常数 = 8.31 J K⁻¹ mol⁻¹。

Temperature in kelvin is obtained from Celsius by: T (K) = θ (°C) + 273.

摄氏温度转开氏温度：T (K) = θ (°C) + 273。

Unit conversions: 1 atm = 101325 Pa; 1 dm³ = 1 × 10⁻³ m³. Always convert to SI units before using the equation.

单位换算：1 atm = 101325 Pa；1 dm³ = 1 × 10⁻³ m³。使用方程前务必将所有量转换为 SI 单位。

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5. Enthalpy Change Calculations | 焓变计算

The heat energy transferred in a reaction can be measured by calorimetry. The heat absorbed or released by the surroundings (usually water or a solution) is:

反应中的热能变化可通过量热法测定。环境（通常是水或溶液）吸收或释放的热量为：

q = mcΔT

where m is the mass of the solution (g), c is the specific heat capacity (4.18 J g⁻¹ K⁻¹ for water), and ΔT is the temperature change (K or °C).

其中 m 为溶液质量 (g)，c 为比热容（水为 4.18 J g⁻¹ K⁻¹），ΔT 为温度变化 (K 或 °C)。

The enthalpy change of the reaction, ΔH, is then calculated using:

反应的焓变 ΔH 由下式计算：

ΔH = –q / n

The negative sign reflects that the system loses energy in an exothermic reaction. To obtain ΔH in kJ mol⁻¹, convert q from J to kJ by dividing by 1000:

负号表明系统在放热反应中损失能量。为得到以 kJ mol⁻¹ 表示的 ΔH，需将 q 从 J 转换为 kJ（除以 1000）：

ΔH = –(mcΔT / 1000) / n

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6. Hess’s Law | 盖斯定律

Hess’s law states that the total enthalpy change of a reaction is independent of the route taken, provided initial and final conditions are the same.

盖斯定律指出，无论反应途径如何，只要始终态相同，总焓变不变。

Using standard enthalpy changes of formation (ΔH_f°):

利用标准生成焓变 (ΔH_f°)：

ΔH° = ΣΔH_f°(products) – ΣΔH_f°(reactants)

Using standard enthalpy changes of combustion (ΔH_c°):

利用标准燃烧焓变 (ΔH_c°)：

ΔH° = ΣΔH_c°(reactants) – ΣΔH_c°(products)

Always balance the equations and use the coefficients when summing. Hess cycles are drawn to visualise the two routes.

叠加时务必配平方程式并使用相应化学计量数。绘制盖斯循环可实现可视化路径。

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7. Reaction Rates | 反应速率

The rate of a reaction describes how quickly a reactant is consumed or a product is formed.

反应速率描述反应物消耗或产物生成的快慢。

Average rate can be expressed as:

平均速率可表示为：

average rate = Δ[A] / Δt

where Δ[A] is the change in concentration of a reactant (mol dm⁻³) and Δt is the time interval (s). Units are typically mol dm⁻³ s⁻¹.

其中 Δ[A] 为反应物浓度变化 (mol dm⁻³)，Δt 为时间间隔 (s)。单位通常为 mol dm⁻³ s⁻¹。

The initial rate is the instantaneous rate at t = 0. It is found from the gradient of the tangent to the concentration–time curve at zero time.

初始速率是 t = 0 时刻的瞬时速率，由浓度–时间

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