Measuring Standard Electrode Potentials | 测量标准电极电势

📚 Measuring Standard Electrode Potentials | 测量标准电极电势

Standard electrode potentials are used to compare the ease with which different half-cells accept electrons. In this article, we look at how these values are measured under standard conditions using the standard hydrogen electrode as a reference.

标准电极电势用于比较不同半电池接受电子的难易程度。本文将介绍如何在标准条件下以标准氢电极为参比来测量这些数值。

1. What Is a Standard Electrode Potential? | 什么是标准电极电势？

The standard electrode potential, E°, of a half-cell is the e.m.f. of a cell made by connecting that half-cell to a standard hydrogen electrode under standard conditions. It is a measure of the reducing or oxidising power of the species in the half-equation.

半电池的标准电极电势 E° 是指该半电池在标准条件下与标准氢电极连接后所构成电池的电动势。它反映了半反应中各物种的还原能力或氧化能力。

By convention, all half-equations are written as reduction processes: oxidised form + n e⁻ ⇌ reduced form. The sign of E° therefore tells us whether the equilibrium lies more to the right than the hydrogen half-equation.

按照约定，所有半反应均写成还原形式：氧化型 + n e⁻ ⇌ 还原型。因此 E° 的正负可以告诉我们该半反应相对于氢半反应更偏向哪一侧。

2. The Standard Hydrogen Electrode (SHE) | 标准氢电极

The standard hydrogen electrode is the reference electrode against which all other standard electrode potentials are measured. It consists of hydrogen gas at 100 kPa bubbling over a platinum electrode immersed in a solution with H⁺ ion activity equal to 1 mol dm⁻³, at 298 K.

标准氢电极是用于测量其他标准电极电势的参比电极。它由 100 kPa 的氢气在 298 K 下通入铂电极表面，铂电极浸在 H⁺ 离子活度为 1 mol dm⁻³ 的溶液中。

Platinum is used because it is inert and provides a surface for the equilibrium: 2H⁺(aq) + 2e⁻ ⇌ H₂(g). The potential of the standard hydrogen electrode is defined as exactly 0.00 V at all temperatures under standard conditions.

使用铂是因为它惰性且能提供表面进行以下平衡：2H⁺(aq) + 2e⁻ ⇌ H₂(g)。在规定标准条件下，标准氢电极的电势被定义为 0.00 V。

The platinum surface is often coated with platinum black to increase its surface area and allow H₂ to adsorb rapidly, helping the equilibrium establish quickly.

铂表面通常镀有铂黑以增加表面积，使 H₂ 能够快速吸附，帮助平衡迅速建立。

3. Standard Conditions for Measurement | 测量的标准条件

To obtain reproducible standard values, measurements must be carried out under agreed standard conditions. These are a temperature of 298 K, a pressure

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