Formula Mass and Mole Concepts of Compounds

The smallest representative unit of a compound is the molecule (or the formula unit), depicted by a chemical formula.

The atomic masses of all atoms in the chemical formula, if added, give the molecular mass (or formula mass) of the compound, measured in atomic-mass-unit.

For example, to find the molecular mass of sucrose or table sugar, the atomic mass of each element is multiplied with the number of atoms of the corresponding element. The sum-total gives the molecular mass of sucrose.

The mass of all molecules (or formula units) present in one mole of a chemical compound is called its molar mass, measured in g/mol.

The molar mass of a compound is numerically equal to its molecular mass (or formula mass). For example, sucrose, with molecular mass of 342.3 amu, will have a molar mass of 342.3 g/mol.

Knowing the actual number of molecules or particles present in a chemical substance is fundamental to understanding its composition, interactions, and combinations.

However, in a given sample of a compound, counting the actual number of molecules by ordinary means is impractical. By employing the relationship between molar mass, mole, and Avogadro’s number, the total molecules present c