Identify the species oxidized and the species reduced in each of these redox equations

A. 3Br2 + 2Ga -> 2GaBr3
B. HCL + Zn -> ZnCl2 + H2
C. Mg + N2 -> Mg3N2

2 answers

Okay so you have to first balance them and then count how much you added or minus in each equation.
Two definitions, only one of which must be memorized. The other you will know is the opposite of what you memorized.

Oxidation is the loss of electrons.
Reduction is the gain of electrons.

I will help you out on the first one.
Br goes from zero on the left to -1 on th right.
Ga goes from zero on the left to +3 on the right.
Here is a site that will help you identify the oxidation state of an element.
http://www.chemteam.info/Redox/Redox-Rules.html