Oxidation Numbers
AlH(SO4)3 and the overall charge is -2
BaCr2O7
2 answers
http://chemistry.about.com/od/generalchemistry/a/oxidationno.htm
Here is a better page.
http://www.chemteam.info/Redox/Redox-Rules.html
http://www.chemteam.info/Redox/Redox-Rules.html