what is the experimental percent of sulfate in alum?

Answer 1

There are several alums; the one most people mean when they speak of "alum" is potassium aluminum sulfate with the formula of KAl(SO4)2.12H2O
%sulfate = (molar mass SO4/molar mass KAl(SO4)2.12H2O)*100 = ??

Answer 2

That sounds about right...

Answer 3

Should be 2x sulfate for the numerator because alum has a subscript of 2 for sulfate.