A 3.455-g sample of a mixture was analyzed for barium ion (Ba2+) by adding a small excess of sulfuric acid (H2SO4) to an aqueous solution of the sample. The resultant reaction produced a precipitate of barium sulfate (BaSO4), which was collected by filtration, washed, dried, and weighed. If 0.2815 g of barium sulfate was obtained, what was the mass percentage of barium in the sample? (Ba = 137.3 g/mol; S = 32.0 g/mol; O = 16.0 g/mol; H = 1.0 g/mol) Ba2+ (aq) + H2SO4 (aq) → BaSO4 (aq) + H2 (g)