A sample of a white solid contains 0.212 g of magnesium and 0.140 g oxygen. What is the empirical formula of this compound?

In determining the empirical formula of a compound, you must convert the mass of each element to moles. Since the given mass for this problem is 0.212 grams of Magnesium and 0.140 grams of Oxygen, just divide the mass by the molar mass of Magnesium (24.305 g/mol) and Oxygen (16 g/mol). You’ll get 0.00872 moles of Magnesium and 0.00875 moles of Oxygen. You then divide the each mole value with the smallest calculated number of moles which is 0.00872. You will get an empirical formula of MgO.