Determine the empirical formula of each of the following compounds if a sample contains c. 87.5% N and 12.5% H by mass.

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Convert the percentage of each element to grams, assuming you have a 100 g sample. This means you have 87.5 g of N and 12.5 g of H.

Convert the mass of each element to moles by dividing by their respective molar masses: N (14.01 g/mol) and H (1.01 g/mol).

Determine the mole ratio of the elements by dividing each element's mole value by the smallest number of moles calculated in the previous step.

If necessary, multiply the mole ratios by a whole number to get whole numbers for each element in the compound.

Write the empirical formula using the whole number mole ratios as subscripts for each element.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

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 percentage composition of each element by mass, allowing chemists to understand the basic composition of a substance without detailing the actual number of atoms in a molecule.

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 the element in the compound by the total mass of the compound and multiplying by 100. This concept is crucial for determining the empirical formula, as it provides the necessary data to find the ratio of elements.

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 10^23) of entities, whether they are atoms, molecules, or ions. This concept is essential for converting mass percentages into moles, which are then used to derive the empirical formula.

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