A chemist decomposes samples of several compounds; the masses of their constituent elements are shown. Calculate the empirical formula for each compound. a. 1.245 g Ni, 5.381 g I b. 2.677 g Ba, 3.115 g Br c. 2.128 g Be, 7.557 g S, 15.107 g O

Stoichiometry is a branch of chemistry that deals with the quantitative relationships between the reactants and products in chemical reactions. It serves as a mathematical method of understanding chemical equations and can predict the amount of product formed from a given amount of reactant, or vice versa. To master stoichiometry, one essential skill is the ability to balance chemical equations, ensuring that the same number of atoms of each element are present on both sides of the equation.

In the context of finding an empirical formula, stoichiometry helps in determining the simplest whole number ratio of atoms within a compound. This is based on the conservation of mass and the concept of the 'mole', which links the mass of substance used in the reaction to the amount of substance in terms of its smallest constituent units, called moles. For complex compounds, understanding stoichiometry allows students not just to calculate the empirical formula but also to understand the underlying reaction mechanisms that form such compounds.

The mole concept is a fundamental aspect of chemistry that facilitates the counting of atoms, molecules, or ions in a given sample. A mole is equivalent to Avogadro's number (\(6.022 \times 10^{23}\) particles) and can be used to convert between the mass of a substance and the number of atoms or molecules it contains.

For empirical formula calculation, the mass of each element is converted to moles using the atomic mass unit (amu), which is defined based on the mass of carbon-12. By dividing the given mass of an element by its atomic mass in amu, students can find the number of moles of each element present in a sample. This conversion is the keystone in the calculation of empirical formulas because it allows for a consistent basis to determine the simplest ratio of atoms, bridging the macroscopic mass with the microscopic atomic count.

Chemical composition refers to the identity and the ratio of the elements that make up a chemical compound. Knowing the composition is crucial because it determines the characteristic properties and behavior of the compound. The empirical formula of a compound provides a simple representation of its chemical composition by showing the simplest whole number ratio of atoms of each element present in the compound.

In practice, when calculating empirical formulas from mass data, it is assumed that the total mass of the compound is the sum of the masses of its constituent elements. After determining the mole ratios, the compound's formula is based on the assumption that the smallest integer ratios reflect the true proportion of elements. Therefore, a solid grasp of chemical composition aids students in predicting how variations in the ratio of elements will affect the overall properties of the compounds they are studying.