The molar mass of a substance is defined as the mass of 1 mol of that substance, expressed in grams per mole, and is equal to the mass of 6.022 × 10 23 atoms, molecules, or formula units of that substance. Mole is a concept that is used to count entities at the microscopic level (i.e., atoms, molecules, particles, electrons, ions, etc). It is the seventh base quantity for the amount of a substance.