Al2(SO4)3(aq) + BaCl2(aq) BaSO4(s) + AlCl3(aq)

Consider the unbalanced equation above. A 0.680 g sample of impure Al2(SO4)3 reacts with excess BaCl2. If the sample produces 0.530 g of BaSO4, what is the mass percent of Al2(SO4)3 in the sample?