The Effect of Concentration on Rate of Reaction | 浓度对反应速率的影响

📚 The Effect of Concentration on Rate of Reaction | 浓度对反应速率的影响

In A-Level chemistry, reaction rate is defined as the change in concentration of a reactant or product per unit time. The effect of concentration on rate is explained by collision theory and summarised by rate equations. This article examines how changing concentration affects rate, how reaction order is determined, and how experimental data are collected.

在 A-Level 化学中，反应速率定义为单位时间内反应物或产物浓度的变化。浓度对速率的影响可通过碰撞理论解释，并用速率方程概括。本文讨论浓度变化如何影响速率、如何确定反应级数以及如何采集实验数据。

1. Rate of Reaction and Concentration | 反应速率与浓度

Reaction rate is usually measured as the decrease in concentration of a reactant or the increase in concentration of a product per unit time, with units such as mol dm⁻³ s⁻¹.

反应速率通常以单位时间内反应物浓度的减少或产物浓度的增加来表示，单位为 mol dm⁻³ s⁻¹。

When the concentration of a reactant is increased, there are more particles of that reactant in the same volume. In most cases, this leads to a higher initial rate because successful collisions become more frequent.

当反应物浓度增大时，相同体积内该反应物的粒子数增多。在多数情况下，由于有效碰撞更加频繁，初始速率会升高。

2. Collision Theory | 碰撞理论

For a reaction to occur, reactant particles must collide with kinetic energy equal to or greater than the activation energy Eₐ and with the correct orientation.

要发生反应，反应物粒子必须以大于或等于活化能 Eₐ 的动能碰撞，并且取向正确。

Increasing concentration increases the number of particles per unit volume. Although the fraction of particles with enough energy does not change, the total number of successful collisions per second increases, so the rate increases.

增大浓度会增加单位体积内的粒子数。虽然具有足够能量的粒子比例不变，但每秒有效碰撞的总数增加，因此反应速率增大。

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

For a reaction with reactants A and B, the relationship between concentration and rate is often written as:

对于反应物 A 和 B 的反应，浓度与速率的关系通常写作：

rate = k[A]ᵐ[B]ⁿ

Here k is the rate constant, and the powers m and n are the orders of reaction with respect to A and B. The orders are determined experimentally and are not generally equal to the stoichiometric coefficients in the balanced equation.

其中 k 是速率常数，指数 m 和 n 分别是对 A 和 B 的反应级数。这些级数由实验确定，通常不等于配平方程式中的化学计量数。

The overall order is the sum m + n. The units of k depend on the overall order, so the rate constant units provide a useful check.

总级数为 m + n。k 的单位取决于总级数，因此速率常数的单位可用来检验反应级数。

4. Zero, First and Second

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