Kinetics II: Rate Equations and the Arrhenius Equation | 动力学 II：速率方程与阿伦尼乌斯方程

📚 Kinetics II: Rate Equations and the Arrhenius Equation | 动力学 II：速率方程与阿伦尼乌斯方程

In Kinetics II, Edexcel A-Level Chemistry moves from qualitative ideas about collision theory to the quantitative description of reaction rates. This article covers rate equations, orders of reaction, the Arrhenius equation, activation energy, reaction mechanisms and practical methods such as clock reactions.

在动力学 II 中，Edexcel A-Level 化学从碰撞理论的定性认识转向了反应速率的定量描述。本文将涵盖速率方程、反应级数、阿伦尼乌斯方程、活化能、反应机理以及时钟反应等实验方法。

1. Rate Equations | 速率方程

A rate equation expresses reaction rate as a function of reactant concentrations. For a reaction aA + bB → products, the rate equation has the form:

速率方程将反应速率表示为反应物浓度的函数。对于反应 aA + bB → 产物，速率方程的形式为：

rate = k[A]^m[B]^n

Here, k is the rate constant, [A] and [B] are concentrations in mol dm⁻³, and m and n are the orders of reaction with respect to A and B. The orders are determined experimentally, not from the balanced equation, and they may be zero, integers or even fractions for some complex reactions.

其中 k 是速率常数，[A] 和 [B] 是浓度，单位为 mol dm⁻³，m 和 n 分别是反应对 A 和 B 的级数。反应级数由实验确定，而不是从配平方程式中直接读出，并且可能为零、整数，甚至在某些复杂反应中为分数。

2. Orders of Reaction and the Rate Constant | 反应级数与速率常数

If m = 0, the reaction is zero order with respect to A: changing [A] has no effect on rate. If m = 1, the reaction is first order with respect to A: rate is directly proportional to [A]. If m = 2, the reaction is second order: doubling [A] increases the rate by a factor of 2² = 4.

若 m = 0，反应对 A 为零级：改变 [A] 不影响速率。若 m = 1，反应对 A 为一级：速率与 [A] 成正比。若 m = 2，反应对 A 为二级：[A] 加倍会使速率增大到 2² = 4 倍。

The overall order is the sum m + n. The rate constant k is temperature-dependent but concentration-independent; a larger k means a faster reaction at the same concentrations. For example, if rate = k[A][B]², the overall order is 3: first order in A and second order in B.

总级数为 m + n 之和。速率常数 k 与温度有关而与浓度无关；在相同浓度下，k 越大表示反应越快。例如，若 rate = k[A][B]²，则总级数为 3：对 A 为一级，对 B 为二级。

3. Units of the Rate Constant | 速率常数的单位

Rate is normally measured in mol dm⁻³ s⁻¹, while concentrations are in mol dm⁻³. Since the overall order changes how many concentration terms multiply together, the units of k also change.Published by TutorHao | A-Level Revision Series | aleveler.com

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