Question

Determine the empirical formula of ibuprofen based on its mass percent composition: C 75.69%, H 8.80%, O 15.51%. Express your answer as the empirical formula of ibuprofen

Answer 1

The empirical formula of ibuprofen, based on its mass percent composition, is C6H9O, derived from converting mass percentages to moles and simplifying to the smallest whole number ratios.

Step-by-step explanation:

To determine the empirical formula of ibuprofen, we consider a hypothetical 100-gram sample based on the mass percent composition provided: 75.69% carbon (C), 8.80% hydrogen (H), and 15.51% oxygen (O).


We convert these percentages to grams which are then converted to moles by dividing by the respective atomic masses of each element (approximately 12.01 g/mol for C, 1.01 g/mol for H, and 16.00 g/mol for O).

1. Calculate moles of carbon: (75.69 g C / 12.01 g/mol) = 6.30 moles C.
   
2. Calculate moles of hydrogen: (8.80 g H / 1.01 g/mol) = 8.71 moles H.
   
3. Calculate moles of oxygen: (15.51 g O / 16.00 g/mol) = 0.97 moles O.

We then divide each mole value by the smallest number of moles calculated to obtain the simplest whole number ratio:

1. Ratio for carbon: 6.30 / 0.97 = 6.49, rounded to 6.
   
2. Ratio for hydrogen: 8.71 / 0.97 = 8.98, rounded to 9.
   
3. Ratio for oxygen: 0.97 / 0.97 = 1.

Thus, the empirical formula for ibuprofen based on its mass percent composition is C6H9O.