氧化还原反应Redox

得电子的物质是氧化剂，自身被还原；失电子的物质是还原剂，自身被氧化（口诀“升失氧，降得还”）。反应可拆成两个半反应，配平时使得失电子数相等。反应能否自发进行可由电极电势判断：E°(氧化剂) > E°(还原剂) 时反应自发，ΔG° = −nFE°。

The substance that gains electrons is the oxidising agent and is itself reduced; the one that loses electrons is the reducing agent and is itself oxidised (OIL RIG: oxidation is loss, reduction is gain). A reaction splits into two half-reactions, balanced so that electrons lost equal electrons gained. Spontaneity follows from electrode potentials: the reaction proceeds when E°(oxidant) > E°(reductant), with ΔG° = −nFE°.

最初“氧化”专指物质与氧结合，“还原”指金属氧化物失去氧变回金属，源于拉瓦锡的燃烧理论。19 世纪扩展为得失氢。1897 年汤姆孙发现电子后，20 世纪初人们用电子转移统一解释氧化还原，并引入化合价（氧化数）的概念，使其涵盖不含氧的反应，如 2 Na + Cl₂ → 2 NaCl。

Originally oxidation meant combining with oxygen and reduction meant a metal oxide losing oxygen to give back the metal, ideas rooted in Lavoisier's theory of combustion. In the nineteenth century the terms were extended to losing and gaining hydrogen. After Thomson discovered the electron in 1897, early-twentieth-century chemists unified redox as electron transfer and introduced oxidation numbers, so it also covers oxygen-free reactions such as 2 Na + Cl₂ → 2 NaCl.

氧化还原反应遍布自然与工业：金属冶炼、电池与电解、燃烧供能、金属腐蚀、漂白消毒；生物体内的呼吸作用和光合作用都是一系列氧化还原过程。分析化学中的高锰酸钾法、碘量法等氧化还原滴定也以此为基础。

Redox reactions are everywhere: smelting metals, batteries and electrolysis, combustion, corrosion, bleaching and disinfection; respiration and photosynthesis are chains of redox steps. Redox titrations in analytical chemistry, such as permanganometry and iodometry, rest on the same principles.