Question

which of the following best describes the difference between molar mass and formula weight?

○ formula weights are measured in grams per mole, while molar masses are measured in atomic mass units.

○ a formula weight is the mass of one molecule or formula unit while a molar mass is the mass of one mole of molecules or formula units.

○ molar masses only describe the mass of ionic compounds, while formula weights can describe any compound.

○ there is no difference between molar masses and formula weights.

Explanation:

1. Analyze the first option: Formula weight is in atomic mass units (amu), molar mass in g/mol. So this option is reversed, incorrect.
2. Analyze the second option: Formula weight is the mass of one molecule/formula unit (in amu), molar mass is mass of one mole (in g/mol). This matches the definitions.
3. Analyze the third option: Molar mass applies to any compound (molecular or ionic), formula weight also applies to any (molecular: molecular weight, ionic: formula weight). So this is incorrect.
4. Analyze the fourth option: There is a difference (units and scale), so incorrect.

Answer:

B. A formula weight is the mass of one molecule or formula unit while a molar mass is the mass of one mole of molecules or formula units.