Chapter 8

Another common type of reaction is called Oxidation-Reduction or abbreviated as REDOX Oxidation – Reaction in which a substance loses electrons. Also, a gain of O atoms. Also, a loss of H atoms. Examples: N2 + O2  2 NO (N2 gained O atoms and is oxidized.) 2H2 + O2  2 H2O (H2 gained O atoms and is oxidized; also, H2 went from 0 charge to +1, losing an electron, again showing it is oxidized.) CH4 + 2 O2  CO2 + 2 H2O (CH4 lost H, and gained O, therefore it is oxidized)

Reduction – Reaction in which a substance gains electrons Reduction – Reaction in which a substance gains electrons. Also, a loss of O atoms or a gain of H atoms. N2 + O2  2 NO (O2 lost O atoms and is reduced.) 2H2 + O2  2 H2O (O2 gained H atoms and is reduced. Also, O2 went from 0 charge to -2, gaining 2 electrons, again showing it is reduced.) CH4 + 2 O2  CO2 + 2 H2O (O2 gained H and therefore it is oxidized) Oxidation cannot occur without reduction occurring at the same time. If one substance loses electrons then another substance has to gain those electrons.

In Summary Figure 08-02 Title: Oxidation–Reduction Reactions Caption: Three different views of oxidation and reduction. Keywords: oxidation, reduction, reaction, electrons 4

Oxidizing agent – Substance that causes oxidation to take place Oxidizing agent – Substance that causes oxidation to take place. It is reduced. Reducing agent – Substance that causes reduction to take place. It is oxidized.

08_03-01un.JPG Figure 08-03-01un Caption: The reducing agent is the substance being oxidized; the oxidizing agent is the substance being reduced. 6

Rusting of metals is a REDOX reaction; the metal is oxidized by the O2 in the air. One important modern application of REDOX reactions are batteries. Each different type of battery is based on different chemical reactions. When the reactants are used up, the battery no longer produces electricity. Some of these reactions can be reversed simply by putting electricity into the battery, thus returning the battery to its original condition so that it can work again. These are called rechargeable batteries.

08_06.JPG Figure 08-06 Title: A Zinc-carbon Cell Caption: Cross section of a zinc-carbon cell. Keywords: zinc-carbon cell, half-reaction, oxidation, anode, reduction, cathode 9

There are many oxidation-reduction reactions in our bodies There are many oxidation-reduction reactions in our bodies. Many are beneficial but some are harmful. By taking certain chemicals as additives, either naturally or artificially, called antioxidants, we can prevent harmful oxidation reactions from taking place, at least to some extent. Two of the most common antioxidants in our diets are Vitamins C and E.