Which term describes the mass in grams of one mole of a substance?

• A. Avogadro's number
• B. Mole
• C. Molar mass
• D. Average atomic mass

Answer: (C)

Molar mass describes the mass in grams of one mole of a substance. It directly links amount of substance to mass, so one mole of any substance weighs its molar mass in grams. For elements, the molar mass in g/mol is numerically equal to the atomic mass in amu when expressed per mole; for compounds, you add the atomic masses of all constituent atoms according to their subscripts to get the molar mass. Avogadro's number is the number of particles in a mole, not a mass. The mole is the unit of amount of substance, not a mass, and average atomic mass is the mass of a single atom in amu, not the mass per mole. So the term describing the mass in grams of one mole is molar mass.