📚 Electrochemistry | 电化学
Electrochemistry connects redox reactions to electron transfer and electrical energy. It includes galvanic cells, which produce electricity from spontaneous reactions, and electrolytic cells, which use electricity to drive non-spontaneous changes. Understanding electrode potentials allows chemists to predict reaction feasibility, design batteries, and control corrosion.
电化学将氧化还原反应与电子转移和电能联系起来。它包括利用自发反应产生电能的伽伐尼电池，以及利用电能驱动非自发变化的电解池。理解电极电势使化学家能够预测反应可行性、设计电池并控制腐蚀。
1. Redox Fundamentals | 氧化还原基础
Oxidation is the loss of electrons, and reduction is the gain of electrons. A useful memory aid is OIL RIG: Oxidation Is Loss, Reduction Is Gain. In any redox reaction, oxidation and reduction occur simultaneously because electrons are transferred from one species to another.
氧化是失去电子，还原是得到电子。一个有用的记忆方法是 OIL RIG：氧化是失电子，还原是得电子。在任何氧化还原反应中，氧化和还原同时发生，因为电子从一种物质转移到另一种物质。
Oxidation states are bookkeeping numbers assigned to atoms using rules: free elements have oxidation state 0; monatomic ions have their charge; oxygen is usually −2 except in peroxides; hydrogen is usually +1 except in metal hydrides; the sum of oxidation states equals the overall charge.
氧化态是根据规则分配给原子的记账数字：游离元素为 0；单原子离子等于其电荷；氧通常为 −2，过氧化物除外；氢通常为 +1，金属氢化物除外；氧化态总和等于总电荷。
The oxidising agent is the species that accepts electrons and is reduced; the reducing agent donates electrons and is oxidised. For example, in Zn + Cu²⁺ → Zn²⁺ + Cu, Zn is the reducing agent and Cu²⁺ is the oxidising agent.
氧化剂是接受电子并被还原的物质；还原剂提供电子并被氧化。例如，在 Zn + Cu²⁺ → Zn²⁺ + Cu 中，Zn 是还原剂，Cu²⁺ 是氧化剂。
2. Balancing Redox Equations with Half-Reactions | 用半反应配平氧化还原方程式
In acidic solution, balance half-equations by: balancing atoms other than O and H; adding H₂O to balance O; adding H⁺ to balance H; and adding electrons to balance charge. The two half-equations are then multiplied so that electron transfer is equal and added together.
在酸性溶液中，配平半反应的方法是：先配平 O 和 H 以外的原子；加 H₂O 配平 O；加 H⁺ 配平 H；再加电子配平电荷。然后将两个半反应乘以适当系数使电子数相等，再相加。
For the reaction between manganate(VII) and iron(II), the half-equations are:
对于高锰酸根离子与铁(II)离子的反应，半反应为：
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O
Fe²⁺ → Fe³⁺ + e⁻
Multiply the iron half-equation by 5 and add to cancel the electrons:
将铁半反应乘以 5 后相加以抵消电子：
MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 4H₂O + 5Fe³⁺
In alkaline solution, any H⁺ can be neutralised by adding OH⁻ to both sides, converting H⁺ and OH⁻ into H₂O.
在碱性溶液中，可以在两边加 OH⁻ 中和 H⁺，将 H⁺ 与 OH⁻ 转化为 H₂O。
3. Galvanic
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