A compound is 2. 00% H by mass, 32. 7% S by mass, and 65. 3% O by mass. What is its empirical formula? The final step is to use the mole ratios of the elements to write the empirical formula. The mole ratios of the elements are: mole ratio of H:S:O = 2:1:4 The mole ratios show the ratios of the elements in the compound. Use these ratios to identify the subscripts on each element in the empirical formula. Remember that the subscript 1 is not shown. What is the correct empirical formula for this compound? HSO H2S1O4 H2SO4.