What are the empirical formulas of substances with the following mass percent compositions? (a) Aspirin: 4.48% H, 60.00% C, 35.52% O

Verified step by step guidance

1. Step 1: Assume you have 100 grams of the compound. This makes the mass of each element equal to its percentage composition.
2. Step 2: Convert the mass of each element to moles by dividing by the atomic mass of each element. For example, moles of H = mass of H / atomic mass of H.
3. Step 3: Determine the mole ratio of the elements by dividing each element's mole value by the smallest number of moles calculated in Step 2.
4. Step 4: If necessary, multiply the ratios by a whole number to get whole numbers for each element in the formula.
5. Step 5: Write the empirical formula using the whole number ratios as subscripts for each element.

Key Concepts

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 of the elements, which is converted into moles to find the ratio. This formula does not provide information about the actual number of atoms in a molecule but rather the relative proportions of each element.

Mole Concept

The mole concept is a fundamental principle in chemistry that relates the mass of a substance to the number of particles it contains. One mole of any substance contains Avogadro's number (approximately 6.022 x 10²³) of entities, whether they are atoms, molecules, or ions. This concept is essential for converting mass percent compositions into moles, which is necessary for determining the empirical formula.

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 a sample by the total mass of the sample and multiplying by 100. Understanding mass percent composition is crucial for determining the empirical formula, as it provides the initial data needed to convert to moles and establish the ratios of the elements.