Determine the empirical and molecular formulas of each of the following substances. For example, butane has an empirical formula of C2H5 (lowest whole-number ratio) and a molecular formula of C4H10, where the molecular formula corresponds to the molar mass of 58.12 g/mol.

Ibuprofen, a headache remedy, contains 75.69% C, 8.80% H, and 15.51% O by mass and has a molar mass of 206 g/mol.

Empirical formula of ibuprofen :

Molecular formula of ibuprofen :

Explanation:

Let the empirical formula of ibuprofen be =

Considering 100 gram of ibuprofen with 75.69% C, 8.80% H, and 15.51% O.

Mass of carbon =

Moles of carbon =

Mass of hydrogen =

Moles of hydrogen =

Mass of oxygen =

Moles of oxygen =

For empirical formula, divide the lowest value of moles from each moles of element present in the compound.

Carbon =

Hydrogen =

Oxygen =  

Empirical formula of ibuprofen :

Molecular mass = n × empirical mass

Empirical mass of ibuprofen=

Molecular mass of ibuprofen = 206 g/mol

206 g/mol = n × 206 g/mol

n = 1

Molecular formula =

Molecular formula of ibuprofen :

=