The key principle here is to find the mole ratio of each element to know the empirical formula. First we need to convert the mass to moles by using the molar mass of each element. The molar mass of S is 32 and O is 16 grams/mole. The moles of S and O given the mass is 0.03125 and 0.09375 moles, respectively. The compound would need 3 moles of O per S. the compound is SO3