Final answer:
The sum of the masses of each atom in the formula of a gas measured in atomic mass units is referred to as molar mass.
Step-by-step explanation:
The sum of the masses of each atom in the formula of a gas measured in atomic mass units is referred to as molar mass. Molar mass is the mass of 1 mole of a substance and is expressed in grams per mole. It can be calculated by adding up the atomic masses of the atoms in the chemical formula.