Page 374 - Chemistry eBook

How to Write Half Reactions 2 (Oxidation)
2. To find the oxidation half reaction:
a. Check which elements underwent oxidation (the oxidation numbers increased).
Mg0 + Cl20 Mg+2Cl2-1
(LEO right ): In oxidation, the oxidation number goes up. Mg started out as Mg0 and ended up as Mg+2. So Mg underwent oxidation.
b. Write out the oxidation half reaction:
Show just the oxidation portion of the equation. Then, place the electrons (that were lost) on the right side of the equation (LEO right).
Mg0 Mg+2 + 2e-
This is the half reaction for oxidation.
There are many Regents questions based on this topic.
373 © UNIT 10: OXIDATION & REDUCTION