What is the molecular formula of each of the following compounds? (a) empirical formula HCO₂, molar mass = 90.0 g/mol

Key Concepts

Empirical Formula

The empirical formula represents the simplest whole-number ratio of atoms in a compound. For example, the empirical formula HCO2 indicates that for every one carbon atom, there are two oxygen atoms and one hydrogen atom. It does not provide information about the actual number of atoms in a molecule, which can be determined by the molecular formula.

Molecular Formula

The molecular formula gives the actual number of each type of atom in a molecule of a compound. It is derived from the empirical formula by multiplying the subscripts by a whole number, known as the molecular weight factor, which is determined by dividing the compound's molar mass by the molar mass of the empirical formula.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in the molecular formula. In this case, knowing the molar mass (90.0 g/mol) allows us to find the molecular formula by comparing it to the molar mass of the empirical formula, which is essential for determining the correct molecular structure.