Molar Mass

A mole of a substance is defined as the amount of that substance equivalent to 6.022 x 10²³ numbers of that thing.  This number is Avogadro’s number.   

For example, one mole of water would be 6.022 x 10²³ molecules of water, one mole of hydrogen would be 6.022 x 10²³ atoms of hydrogen, and one mole of a basketball would be 6.022 x 10²³ basketballs (that’s a lot of basketballs!).   

The molar mass, therefore, is the mass of one mole of the substance.  On the scale of atoms, the mass of an individual atom (atomic mass) is measured in atomic mass units (amu).  When scaled to Avogadro’s number, this translates to one gram per mole of that substance.  For example, the mass of one hydrogen atom is one amu.  Scaling by Avogadro’s number, the molar mass of hydrogen is, therefore, one gram per mole.