Calculate in which of their oxides the mass fraction is greater than BaO Al2O3.

Mass fraction – the percentage of an element in a compound. So there is a compound BaO weighing 153 grams per mole. The mass of this compound can be determined by adding the mass of oxygen to the mass of barium: 137 + 16 = 153; the mass of each element can be found on the periodic table. There is a compound of barium oxide, weighing 153 grams, this compound has 100%, and oxygen in it is X%. Hence x = 100 * 16/153; X = 10.5%. The compound contains 10.5% oxygen and, consequently, 100% – 10.5% = 89.5% barium. For the same scheme, we consider the mass fraction of oxygen in combination with aluminum: m (Al2O3) = 102 grams and this is 100%, and m (O) 3 = 48 grams. Hence, x = 48 * 100/102; X = 47%.