The mass percent of oxygen in Barium perchlorate is is 38%.
The molecular mass of Barium perchlorate (Ba(ClO4)2) is 336.2282 g/mol. Percent composition of Oxygen will be = [(Molecular mass of Oxygen X 8)/ Molecular mass of Barium perchlorate] X 100% = [(15.99 X 8)/336.2282] X 100% = 38%
