Total mass of oxide z2o3 is 0.797g mass of element z in the oxide is 0.422g therefore, mass of oxygen in the oxide is 0.797 - 0.422 = 0.375 g Number of moles of oxygen in the oxide = 0.375/16 = 0.02344 (atomic mass of oxygen=16) From the given chemical formula of oxide, we know that, the element z and oxygen are in the ratio of 2:3. So, number of moles of z is 0.02344 *2/3 = 0.015625 Hence, atomic mass of z should be = 0.422/0.015625 = 27 Element with atomic mass 27 is Aluminium. The oxide is Al2o3
