posted by shelly on .
a compound with the molecular weight of 276 grams was determined to be 39.10% carbon, 8.77% hydrogen, and 52.13% oxygen. what is the empiricial formula and the molecular formula for the compound? i do not know where to start!
Start by taking a 100 gram sample. That will give you
39.10 g C
8.77 g H
52.13 g O.
Convert each to moles. moles = grams/molar mass.
Then fin the ratio of each with small whole numbers. The easiest way to do that is to divide the smallest number of moles by itself. That will give you 1.00 for that element, then divide all of the other moles by that same small number. That will give you the empirical formula. To fin the molecular formula, find the empirical formula mass by adding the atomic masses of the elements. The molecular formula will be a multiple of that number. Post your work if you get stuck.