Answer to Question #70513 in Physical Chemistry for alyssa

Question

Describe how oxidation and reduction involve electrons, change oxidation numbers, and combine in oxidation-reduction reactions.

Answer 1

During oxidation-reduction reaction electrons transfer from one atom to another, namely from the atoms of an element which is oxidized to the atoms of an element which is reduced. Oxidation number of the element which is oxidized increases. Oxidation number of the element which is reduced decreases. Oxidation and reduction reactions are two half-reactions that are to be combined. In order to combine the two half-reactions we must make sure that the number of electrons in each half-reaction is equal. For example, let’s consider the reaction:

Sn + Cl2 ---> Sn2+ + 2Cl¯

Electrons transfer from Sn to Cl . Oxidation number of Sn increases from 0 to 2+. Oxidation number of Cl decreases from 0 to 1-. Let’s write down the two half-reactions:

Cl2 + 2e¯ ---> 2Cl¯
Sn ---> Sn 2+ + 2e¯

The number of electrons in each half-reaction is equal. The two half-reactions are combined.