A compound has a molecular mass of approximately 295 g. It contains 40.68% Carbon, 5.12% Hydrogen, and 54.20% Oxygen. Calculate the empirical and molecular formula.
To find the empirical formula, we want to find the moles of each element and then reduce them to the smallest whole number. When given % as in this problem, it is easiest to just assume we have 100 g of the unknown, and then % becomes grams. C: 40.68 g x 1 mol C/12 g = 3.39 moles C H: 5.12 g H x 1 mol H/1 g = 5.12 moles H O: 54.20 g O x 1 mol O/16 g = 3.39 moles O Note that C and O have the same number of moles, so they will have the same number in the empirical formula. However, H has more moles. If we divide all by 3.39 we get 1 mol C 1 mol O 1.5 mol H (still not a whole number, but we can now multiply all by 2) Final answer... 2 mol C 2 mol O 3 mol H Empirical formula (arrange in order of C, H, O) = C2H3O2
