Oxidation Numbers:
My question to you is how did Al get a +3 Oxid.#, and S got 6... What is the mathematical explanation for that. I understand the rules that O is almost always -2 for its' oxid #.
Would O be 10 bc you'd multple 4*3 and minus 2?
3 answers
What compound are you thinking of?
Aluminum sulfate!
Al is in group IIIA and is +3, I think, almost always. But you can tell by looking at the formula of Al2(SO4)3. The tells you oxidation number of Al is +3 and the 2 tell you the sulfate ion is -2. How to do S.
Al is 2*+3 each = +6.
O is 12*-2 = -24
Remember Al2(SO4)3 is zero overall.
So 2*Al + 12*O + 3S = 0
6 + (-24) + 3S = 0
3S = 18
S = +6
Voila
Another way.
You know SO4 polyatomic ion is -2
4*O is -8 so S must be +6 to leave a -2 charge on the ion.
Al is 2*+3 each = +6.
O is 12*-2 = -24
Remember Al2(SO4)3 is zero overall.
So 2*Al + 12*O + 3S = 0
6 + (-24) + 3S = 0
3S = 18
S = +6
Voila
Another way.
You know SO4 polyatomic ion is -2
4*O is -8 so S must be +6 to leave a -2 charge on the ion.
1 answer