Weak Acids – Using the Acid Dissociation Constant Kₐ | 弱酸——酸解离常数 Kₐ 的应用

📚 Weak Acids – Using the Acid Dissociation Constant Kₐ | 弱酸——酸解离常数 Kₐ 的应用

Weak acids do not fully ionise in aqueous solution. Their equilibrium behaviour is quantified by the acid dissociation constant, Kₐ, which allows chemists to compare acid strengths and to calculate pH or concentrations from equilibrium data.

弱酸在水溶液中不能完全电离。它们的平衡行为可以用酸解离常数 Kₐ 定量描述，借此可以比较酸性强弱，并由平衡数据计算 pH 或浓度。

1. What Is a Weak Acid? | 什么是弱酸？

A weak acid is a proton donor that only partially dissociates in water. Instead of going to completion, the dissociation reaches a dynamic equilibrium between the undissociated acid molecules and the ions formed.

弱酸是一种在水中只部分解离的质子给体。解离反应不会进行到底，而是在未解离的酸分子和生成的离子之间达到动态平衡。

HA(aq) + H₂O(l) ⇌ H₃O⁺(aq) + A⁻(aq)

For A-level calculations, the equilibrium is usually simplified to:

在 A-level 计算中，通常将平衡简化为：

HA(aq) ⇌ H⁺(aq) + A⁻(aq)

This means an equilibrium mixture contains

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