J.R. S. answered 04/15/21
Ph.D. University Professor with 10+ years Tutoring Experience
Aluminum sulfate comes from the reaction of aluminum hydroxide and sulfuric acid. The cation comes from the base (aluminum hydroxide) and the anion comes from the acid (sulfuric acid).
Balanced neutralization reaction:
2Al(OH)3(aq) + 3H2SO4(aq) ==> Al2(SO4)3 + 6H2O
....base.........+....acid.....................salt.........+ ...water