Here is a good site to learn how to do these. Oxygen is -2 for each atom.
http://www.chemteam.info/Redox/Redox-Rules.html
Consider the following substance:
Al2(SO4)3
What is the oxidation number of:
a) aluminum
b) sulfur
c)oxygen
2 answers
<<<<<<<<<<>>>>>>>>>>>>
First : Al in III A
>>>> Al = 3+
Second : O must be 2-
Third : count and S = 6+
First : Al in III A
>>>> Al = 3+
Second : O must be 2-
Third : count and S = 6+
1 answer