1. Determine the Empirical Formula
* Convert percentages to grams: Assume you have 100 g of the compound. This means you have 70.6 g C, 5.9 g H, and 23.5 g O.
* Convert grams to moles: Divide each mass by the respective element's molar mass:
* C: 70.6 g / 12.01 g/mol = 5.88 mol
* H: 5.9 g / 1.01 g/mol = 5.84 mol
* O: 23.5 g / 16.00 g/mol = 1.47 mol
* Find the simplest whole-number ratio: Divide each mole value by the smallest mole value (1.47 mol):
* C: 5.88 mol / 1.47 mol = 4
* H: 5.84 mol / 1.47 mol = 4
* O: 1.47 mol / 1.47 mol = 1
* The empirical formula is C₄H₄O
2. Determine the Molecular Formula
* Calculate the empirical formula mass: (4 x 12.01 g/mol) + (4 x 1.01 g/mol) + (1 x 16.00 g/mol) = 68.06 g/mol
* Find the ratio between the molecular weight and the empirical formula mass: 136 amu / 68.06 g/mol = 2
* Multiply the subscripts in the empirical formula by this ratio: C₄H₄O x 2 = C₈H₈O₂
Therefore, the molecular formula of the compound is C₈H₈O₂.
