Alaboratory analysis of vanillin, the flavoring agent in vanilla, determined the mass percent composition: c, 63.15%; h, 5.30%; o, 31.55%. determine the empirical formula of vanillin.

C8H8O3 Lookup the atomic weights of the elements involved: Atomic weight carbon = 12.0107 Atomic weight hydrogen = 1.00794 Atomic weight oxygen = 15.999 Now determine the relative moles of each element by dividing the weight percentage by the atomic weight of each element. Carbon = 63.15 / 12.0107 = 5.257811784 Hydrogen = 5.30 / 1.00794 = 5.258249499 Oxygen = 31.55 / 15.999 = 1.97199825 So we have a ratio of carbon : hydrogen : oxygen of 5.257811784 : 5.258249499 : 1.97199825 We want to create a ratio of small integers that comes close. So start by dividing all the numbers by the smallest. Getting: 2.666235523 : 2.666457488 : 1 Not quite there. We could multiply the above values by 1, 2, 3, etc until we get some values close to integers, but the .666 values looks rather close to 2/3, so let's multiply the values by 3 and see what we get. 7.998706568 : 7.999372463 : 3 And this looks good. The ratio looks to be 8:8:3 So the empirical formula is C8H8O3