How to find the empirical formula?

How do you find the empirical formula of an unknown compound?

• Here are the elements and mass percentages: Carbon: 62% Hydrogen: 10% Oxygen: 28% Maybe someone can tell me where I'm going wrong. I'm treating the percentages as actual values of a 100g sample and then converting those gram values to mole values. I end up with 5.1619 moles of carbon, 9.9212 moles of hydrogen, and 1.7501 moles of oxygen. From there, I divide the moles of oxygen into the other values to try to find the correct proportions of each element. Does this sound right? I can't seem to find a ratio. Can anyone figure out the empirical formula?

• Answer:

  Everything that you have done in your solution technique is correct. C ---> 5.1619 / 1.7501 = 2.95 H ---> 9.9212 / 1.7501 = 5.67 O ---> 1.7501 / 1.7501 = 1 The 2.95 rounds to 3, but the 5.67 is a problem. So, do this: C ---> 9/3 H ---> 17/3 O ---> 3/3 Multiply by three to get this empirical formula: C9H17O3 Good problem. More empirical formula stuff here: http://www.chemteam.info/Mole/Mole.html Look under problem sets.