Replacing fossil fuels with biomass is important for many uses beyond energy production. Compounds derived from biomass may be useful as starting materials for many chemical processes. Nitroanaline had been observed in experiments on biomass from pine needles and can be used as a precursor for pharmaceuticals. It contains 52.17% carbon, 4.38% hydrogen, 20.28% nitrogen, and 23.17% oxygen by mass. Determine the empirical formula of nitroanaline.

Strategy The empirical formula is based on the mole ratios among the elements in the compound, and the data given are in terms of mass. Molar mass provides the link between mass and moles, as usual. We can begin by choosing a convenient mass of the compound—usually 100 g—and use the percentages given to find the mass of each element in that sample. Then we will convert those masses into numbers of moles of each element. The ratios between those numbers of moles must be the same for any sample of the compound. Finally, we will need to convert those ratios into whole numbers to write the empirical formula.