Posted by Jay on .
what will be the mass of angydrous Alum left over if one starts with 100.00 g of hydrated Alum?
please can you explain what fraction do I need to use. Based on the given information I can find the %theoretical of water in angydrous Alum. But I still don't understand how to solve for left over.

chemisty 
DrBob222,
%H2O = (12*molar mass H2O/molar mass KAl(SO)4)2.12H2O)*100 = ??
% anhydrous alum = 100  %H2O
fraction anydrous alum = % anhydrous alum/100.
grams anhydrous alum in 100 g alum = 100g x fraction anhydrous alum.
By the way, there is no water, theoretical or otherwise, in anhydrous alum.