Redox couple

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A redox pair , also known as a corresponding redox pair , is a partial reaction (half reaction) of a redox reaction . In general terms:

,

where Red stands for the reduced , Ox for the oxidized form of a particle ( molecule , atom or ion ) and n for the number of electrons e - .

Read from left to right, Red appears as an electron donor . Reading from right to left, Ox acts as an electron acceptor . Alternatively, one can also speak of reducing and oxidizing agents :

Two redox pairs are required to describe a redox reaction, since there are no free electrons under common chemical conditions. If an electron is formally released in a partial reaction, another partial reaction is required in order to accept the electron:

Examples

As an example one can consider the voluntary conversion of a copper rod in an aqueous solution that contains silver ions. Copper is oxidized and silver is deposited in elemental form by reduction.

The partial reactions can also be more complex. Here it is advantageous to consider the oxidation numbers of the relevant atoms. In an aqueous, acidic solution, sodium nitrite reacts to nitrate when potassium permanganate is added. Permanganations rule to form Mn 2+ ions. In the partial reaction of manganese, the oxidation levels of the manganese are relevant, the oxidation level of the oxygen atoms and the hydrogen atoms remain unchanged.

Individual evidence

  1. ^ Arnold F. Holleman, Nils Wiberg: Textbook of Inorganic Chemistry , 102nd Edition, de Gruyter, Berlin, 2007, p. 218ff.
  2. ^ Karl-Heinz Lautenschläger, Werner Schröter, Joachim Teschner, Hildegard Bibrack, Taschenbuch der Chemie , 18th edition, Harri Deutsch, Frankfurt (Main), 2001, p. 170.