Find Empirical Formula from Percent Composition

Q: A compound is found to have a molar mass of 144.14 g/mol. Upon elemental analysis, it is found to be made up of 50.0% carbon, 5.6% hydrogen and 44.4% oxygen. What is the molecular formula for the compound?

A: Assume that you have 100 g of the substance. Then, you have 50.0 g of carbon, 5.6 g of hydrogen and 44.4 g of oxygen.

To figure out the number of atoms of each that you have, convert these masses into moles:
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So, the ratio of C:H:O is 4.16:5.55:2.78. We need an equivalent ratio in integers. One of my favorite techniques to simplifying the ratio is to divide all of the numbers by the smallest number that appears.
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To get rid of a “.5” that appears, we can simply double all of the values.
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And so we finally have an integer ratio that matches the mole ratio we found earlier. This means we have 3 carbon atoms for every 4 hydrogen atoms and 2 oxygen atoms. In other words, the empirical formula of out compound is C3H4O2. What is this molecule's mass?
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We need the molecular mass of the compound to be DOUBLE this, so double the subscripts in the chemical formula. You will find that the molecule C6H8O4 has a molecular mass of 144.14 g/mol as we need.