What are the empirical formulas of the compounds with the following compositions? (a) 40.1 percent C, 6.6 percent \(H, 53.3\) percent \(O ;\) (b) 18.4 percent \(C\), 21.5 percent \(\mathrm{N}, 60.1\) percent \(\mathrm{K}\)

Stoichiometry is a foundational principle in chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It provides information on the relative amounts of substances needed or produced in a chemical process. To determine these relationships, stoichiometry relies on the mole concept, balanced chemical equations, and the conservation of mass.

When aiming to calculate an empirical formula, stoichiometry comes into play by providing a methodical approach. By treating the percentage composition as a mass ratio in a hypothetical 100 grams of the compound, it becomes possible to directly convert these masses into moles, which are the fundamental counting units in chemistry. From the mole ratios, one can determine the simplest whole number ratio of atoms within a compound, which is the essence of its empirical formula.

The mole concept is a central idea in chemistry that allows chemists to count atoms, molecules, and ions in terms of quantity. A mole is defined as the amount of substance that contains as many entities (such as atoms or molecules) as there are atoms in 12 grams of pure carbon-12, which is approximately 6.022 x 10^23 entities, known as Avogadro's number.

In the context of empirical formula determination, the mole concept is utilized to convert the mass of each element in a compound to the number of moles. This provides a common basis for comparison since atoms have different masses. By dividing the moles of each element by the smallest number of moles obtained in the calculation, we find the ratio that indicates how many atoms of each element are present in the simplest form of the compound.

Molar mass is the mass of one mole of a given substance (chemical element or chemical compound in grams per mole). It is a fundamental property that links the mass of a substance to its moles, enabling the conversion of mass to moles and vice versa. The molar mass of each element is found on the periodic table and is roughly equivalent to the atomic weight of the element.

When calculating the empirical formula, the molar mass is used to convert the percent composition to moles. For instance, to convert from grams to moles, you divide the given mass of each element by its respective molar mass. This step is crucial in finding the ratio of atoms in the compound and thus its empirical formula.

Chemical composition refers to the identity and ratio of the elements that make up a compound. It's expressed in terms of the percentage by mass of each element in the compound. This information is intrinsic to the substance and dictates how it reacts chemically.

In our exercise, percentage composition is given for elements in compounds, which forms the starting point of empirical formula calculation. After converting these percentages to moles using the mole concept and molar masses of the elements, a chemical formula that reflects the simplest whole number mole ratio of the elements in the compound is derived. The resulting empirical formula is the simplest expression of the compound's chemical composition.