L2 - Half-Reactions

A half-reaction is a balanced chemical equation that represents either the loss of gain of electrons by a substance, either atoms become ions or ions become atoms.  It is half of the chemical reaction that allows us to take a closer look at what is happening during the reaction.

In the last lesson we looked at oxidation and reduction, and how they are used to used to determine how the electrons are moving during the reaction.  These two reactions, and the total redox reaction are the basis for half-reactions.The major difference between the last lesson that this lesson (from now on) is that the reactions are always written with the electrons being either added to the reactants, or added to the produces instead of being subtracted from the reactants.

As in other chemical reactions, the net equation must be balanced.  We will use what we have learned so far so that we can learn how to write balanced half-reactions and net equations. 

Read pages 561 - 562 in your textbook.