Molecular Mass

The molecular mass – also called molecular weight (obsolete term) – is the sum of the atomic masses of all atoms of a molecule. In the case of salts, they are called formula mass, because salts are built from ions. A distinction is made between relative molecular mass (has no unit of measurement) and absolute molecular mass (indicated in g, kg or da). The molecular mass must not be confused with the molar mass. The latter expresses the mass per amount of material in g or kg per mole. The numerical value of the relative molecular mass and the molar mass is identical.