To determine the empirical formula of a compound, we divide the given masses to their respective atomic weights. For S, 1.0 g divided by 32 g/mol is 0.03125 mol S; for O, 1.5 gram O divided by 16 g/mol O is equal to 0.09375 mol O. We divide the greater number o mole by less number of mole, that is 0.09325/0.03125 is 3. Hence for S, it is 1 and for O, it is equal to 3. The answer is SO3.