To determine the empirical formula of the compound, we need to find the mole ratio of magnesium to oxygen in the compound. 1. Calculate the moles of magnesium used in the reaction:Magnesium has a molar mass of 24.31 g/mol.moles of Mg = mass of Mg / molar mass of Mgmoles of Mg = 0.25 g / 24.31 g/mol = 0.0103 mol2. Calculate the mass of oxygen in the compound:mass of O = mass of compound - mass of Mgmass of O = 0.73 g - 0.25 g = 0.48 g3. Calculate the moles of oxygen in the compound:Oxygen has a molar mass of 16.00 g/mol.moles of O = mass of O / molar mass of Omoles of O = 0.48 g / 16.00 g/mol = 0.0300 mol4. Determine the mole ratio of magnesium to oxygen:Divide the moles of each element by the smallest number of moles to find the simplest whole number ratio.Mg:O ratio = 0.0103 mol / 0.0103 mol : 0.0300 mol / 0.0103 mol = 1:2.91Since the ratio is close to a whole number ratio of 1:3, we can round it to the nearest whole number.5. Write the empirical formula:The empirical formula of the compound is MgO.