How many moles of o2 - ions are there in 0.350 moles of aluminum oxide, al2o3?

The formula for aluminum oxide is Al2O3, which means that, if aluminium oxide is ionically bonded, every formula mass of aluminum oxide contains three O2 - ions. In this instance,.0350 formula masses of aluminum oxide would contains, 0.350 mole Al2O3 (3 mole O2-/1mole) = 3*0.350 = 1.05 Hence 1.05 moles of O2-. If aluminum oxide were covalently bonded, it would not contain any O2 - ions.