The elemental mass percent composition of ibuprofen (a nonsteroidal anti-inflammatory drug [NSAID]) is 75.69% C, 8.80% H, and 15.51% O. Determine the empirical formula of ibuprofen.

Verified step by step guidance

1. insert step 1> Calculate the moles of each element in a 100 g sample of ibuprofen. Assume you have 100 g of ibuprofen, which means you have 75.69 g of carbon (C), 8.80 g of hydrogen (H), and 15.51 g of oxygen (O).
2. insert step 2> Convert the mass of each element to moles by dividing by their respective atomic masses: \( \text{Moles of C} = \frac{75.69 \text{ g}}{12.01 \text{ g/mol}} \), \( \text{Moles of H} = \frac{8.80 \text{ g}}{1.008 \text{ g/mol}} \), \( \text{Moles of O} = \frac{15.51 \text{ g}}{16.00 \text{ g/mol}} \).
3. insert step 3> Determine the simplest whole number ratio of moles of each element by dividing each by the smallest number of moles calculated in the previous step.
4. insert step 4> If necessary, multiply the ratios by a common factor to obtain whole numbers for each element.
5. insert step 5> Write the empirical formula using the whole number ratios as subscripts for each element.

Key Concepts

Mass Percent Composition

Mass percent composition refers to the percentage by mass of each element in a compound. It is calculated by dividing the mass of each element in one mole of the compound by the total molar mass of the compound, then multiplying by 100. This information is crucial for determining the relative amounts of each element present in a compound, which is the first step in finding the empirical formula.

Empirical Formula

The empirical formula of a compound represents the simplest whole-number ratio of the elements present in that compound. It is derived from the mass percent composition by converting the percentages to moles and then simplifying the mole ratios. The empirical formula does not necessarily reflect the actual number of atoms in a molecule but provides a foundational understanding of the compound's composition.

Mole Conversion

Mole conversion is the process of converting mass or mass percent of an element into moles, which is a fundamental unit in chemistry representing a specific quantity of particles. To find the number of moles, the mass of the element is divided by its molar mass. This conversion is essential for determining the ratios of elements in a compound, which is necessary for calculating the empirical formula.