Mass of one mole of a substance in grams per mole

• A. Avogadro's number
• B. Mass
• C. Molar mass
• D. Atomic weight

Answer: (C)

Molar mass is the mass of one mole of a substance expressed in grams per mole. It links the amount of substance (moles) to its mass in grams, and for a molecule or formula unit it’s found by summing the atomic masses of all atoms in the formula. For elements, the numerical value of molar mass matches the atomic weight, but the molar mass explicitly includes the units g/mol, which is what you use when converting between grams and moles in reactions.

Avogadro's number is the number of particles in a mole, not a mass. Atomic weight is a dimensionless average that describes isotopic composition and is not given in grams per mole, though it coincides numerically with the molar mass of pure elements. So the term that correctly describes the mass of one mole, in the required units, is molar mass. For example, the molar mass of water is about 18.015 g/mol.