Calculate the grams of oxygen in 90.0 g of cl2o

TO calculate the amount in mass of oxygen in the given compound we need data on the molar mass of the compound and oxygen. Also, we relate the number of moles of oxygen per 1 mol of the substance. We do as follows:

90.0 g (1 mol / 86.91 g) (1mol O / 1 mol Cl2O) (16 g / 1 mol) = 16.57 g O