The term molar mass
is used all the time in chemical calculations, so you need to know what it means. First, it is a mass, so it has units of mass, commonly the gram. Second, it concerns the mole (Avogadro's number). Whether you're dealing with elements or compounds, the molar mass of a species is the mass in grams of one mole (6.022 x 1023
) of that species: one mole of atoms, one mole of molecules, or one mole of formula units.
Here's a good example. What is the molar mass of a penny? A single American penny has a mass of about 3 grams. The molar mass of the American penny would be the mass of Avogadro's number of pennies, in grams. Multiplying Avogadro's number by the mass of one penny shows this to be about 2 x 1024
grams. One molar mass of pennies is about 2 x 1024
grams of pennies.