Edexcel A-Level Combined Science 043: Kinetics, Equilibria and Energetics | Edexcel A-Level 综合科学 043：动力学、平衡与能量学

📚 Edexcel A-Level Combined Science 043: Kinetics, Equilibria and Energetics | Edexcel A-Level 综合科学 043：动力学、平衡与能量学

This revision guide covers the core physical chemistry ideas in Edexcel A-Level Combined Science topic 043: measuring rates, the rate equation, activation energy, dynamic equilibrium, equilibrium constants, Le Chatelier’s principle, pH, buffers and enthalpy cycles. Understanding these ideas together is essential for quantitative and qualitative questions on Paper 1 and Paper 2.

本复习指南涵盖 Edexcel A-Level 综合科学主题 043 的核心物理化学概念：反应速率测量、速率方程、活化能、动态平衡、平衡常数、勒夏特列原理、pH、缓冲溶液以及焓变循环。掌握这些概念之间的关联对 Paper 1 和 Paper 2 中的定量与定性题目至关重要。

1. Measuring Reaction Rate | 反应速率的测量

The rate of a chemical reaction is defined as the change in concentration of a reactant or product per unit time. In the laboratory you can follow the rate by measuring gas volume, mass loss, colour intensity or pH change over time.

化学反应速率定义为单位时间内反应物或生成物浓度的变化。在实验室中，你可以通过测量气体体积、质量损失、颜色强度或 pH 随时间的变化来跟踪反应速率。

For a reaction A + B → C, the average rate can be written as:

对于反应 A + B → C，平均速率可以表示为：

rate = −Δ[A]/Δt = −Δ[B]/Δt = +Δ[C]/Δt

• Recording the tangent gradient on a concentration–time graph gives the instantaneous rate at a chosen time.
• 在浓度–时间图上作切线，其斜率给出某一时刻的瞬时速率。
• Initial rate is often used because concentrations are known precisely at t = 0.
• 常用初始速率，因为 t = 0 时浓度已知且更易控制。

2. Rate Equation and Order of Reaction | 速率方程与反应级数

The rate equation links the rate of

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