Molar mass is expressed in which units?

Molar mass is expressed in which units?

• A. Grams per mole
• B. Liters per mole
• C. Moles per liter
• D. Kilograms per mole

Answer: (A)

Molar mass is the mass of one mole of a substance, so its units must express mass per amount of substance. That means mass divided by amount of substance, which in chemistry is commonly grams per mole. Using grams per mole keeps numbers practical (for example, water has a molar mass of about 18.015 g/mol, so one mole weighs ~18 g). Other options describe volume per mole or concentration, which aren’t what molar mass measures. Kilograms per mole is technically valid, but the standard convention in chemistry is g/mol for ease of use.

Molar mass is the mass of one mole of a substance, so its units must express mass per amount of substance. That means mass divided by amount of substance, which in chemistry is commonly grams per mole. Using grams per mole keeps numbers practical (for example, water has a molar mass of about 18.015 g/mol, so one mole weighs ~18 g). Other options describe volume per mole or concentration, which aren’t what molar mass measures. Kilograms per mole is technically valid, but the standard convention in chemistry is g/mol for ease of use.