The compound adrenaline contains \(56.79 \% \mathrm{C}, 6.56 \% \mathrm{H}\), \(28.37 \% \mathrm{O}\), and \(8.28 \% \mathrm{~N}\) by mass. What is the empirical formula for adrenaline?

Understanding the percentage composition of a compound is essential for computing its empirical formula. Percentage composition represents the mass percentage of each element within a compound—a critical starting place for any stoichiometric deduction. For example, if a compound is said to have a carbon content of 56.79%, that means for every 100 grams of the compound, 56.79 grams are carbon.

To determine the empirical formula, the initial step is converting these percentages into a more workable unit—grams. Assuming a 100-gram sample simplifies this process, directly transcribing percentage to gram measurement. Once the masses are established, we can proceed to calculate the actual number of moles of each element in the sample, which is pivotal for finding the empirical formula.

Molar mass is a property of substances that links the mass of a sample to the amount of substance (measured in moles). This cornerstone of chemistry is expressed in grams per mole (g/mol) and is equivalent to the atomic weight of an element or the sum of the atomic weights of elements in a chemical compound. To compute the moles of an element from its mass in a compound, we divide the mass by the molar mass of that element.

For instance, with carbon's molar mass at 12.01 g/mol, 56.79 grams of carbon corresponds to approximately 4.73 moles. Grasping these conversions allows for a seamless translation between the mass of an element and the amount in moles, facilitating the determination of the empirical formula.

The mole ratio is integral in determining the empirical formula of a compound. After translating the mass of each element to moles, the next task involves finding a simple ratio of moles that correlates with whole numbers. The approach is straightforward: identify the smallest number of moles among the elements and divide all mole quantities by this value.

This results in a set of dimensionless numbers that represent the simplest ratio of atoms in the compound. However, it's crucial to round these ratios to the nearest whole number, as atoms in compounds must be represented by integers. These ratios form the subscripts in the empirical formula, shedding light on the fundamental proportions of the constituent elements.

The chemical formula, specifically the empirical formula, reveals the simplest whole-number ratio of atoms within a molecule. Unlike the molecular formula that shows the actual number of atoms, the empirical formula is a reduced form that maintains the original proportions of the component elements.

Once we've identified the mole ratios, we use them as subscripts in the empirical formula. For our adrenaline example, the mole ratio gave us C₈H₁₁O₃N. This indicates that in the most simplified version of adrenaline, there are 8 carbon atoms, 11 hydrogen atoms, 3 oxygen atoms, and 1 nitrogen atom. Remember, the chemical formula is the skeleton of a chemical compound and finding it is crucial for understanding its molecular structure and properties.