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氧化还原滴定

氧化還原滴定(Redox titration)是一種依據滴定液和待測液之間氧化還原反應滴定。氧化還原滴定可能會使用氧化還原指示劑或電位計以標示滴定終點。

示例

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設一氧化還原滴定使用還原劑處理溶液,並使用澱粉作為指示劑。碘和澱粉會形成深藍色絡合物。碘(I2)能被硫代硫酸根離子(S2O32−)等還原成碘離子(I),當碘耗盡,藍色消失。此為碘量滴定(iodometric titration)。

通常碘還原為碘離子是一系列反應的最後步驟。這類起始反應用於將未知量的待測液(欲分析的物質)轉換成等量的碘,以待滴定。有時中間反應會以其他鹵素代替碘,因為它們在標準溶液中更易測量,而且/或者更易與待測液反應。這些額外的步驟在碘量滴定時可能是值得的,因為在當量點時,溶液由藍色轉無色,這相較其他分析方式更為明顯。

這種在水溶液中的反應系列以雷瑣辛為待測液,溴酸鹽為標準液,硫代硫酸鹽為滴定液,澱粉為指示劑,可用以下反應式表示。氧化數已在圓括號中標明。


  1. 酸性溶液 溴酸鹽 + 過量溴化物 + 水。 溴繼續反應至 ii。

  2. 溴 + 雷瑣辛 → 溴化氫 + 三溴間苯二酚。 未反應的溴繼續反應至iii。

  3. 溴 + 過量 → 溴化物 + 。碘繼續反應至iv。

  4. 碘 + 硫代硫酸根離子 → 碘 + 四硫磺酸根離子。

設雷瑣辛和溴酸鹽的起始量為RB,硫代硫酸鹽的量為TBT為已知,R未知,但須確定R小於B。(所有量以莫耳計算)則R = B -T/6

參見

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參考書目

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S. M. Khopkar. Basic Concepts Of Analytical Chemistry. New Age International. 1998年: 42 [2014-05-05]. ISBN 978-1906574000. (原始内容存档于2014-05-05). 

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氧化还原滴定
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