The molar mass of a compound is the mass in grams of 1 mole of that substance, a property expressed in units of grams per mole (g/mol)īecause the definitions of both the mole and the formula mass are based on the same reference substance, 12C, the molar mass of any compound is numerically equivalent to its formula weight in amu. We have defined a mole based on the isotopic atomic mass of carbon-12. The masses of 1 mole of different compunds, however, are different, since the masses of the individual molecules are drastically different. The atomic mass of an element is the relative average of all of the naturally occurring isotopes of that element and atomic mass is the number that appears in the periodic table. 3: Table salt, NaCl, contains an array of sodium and chloride ions combined in a 1:1 ratio.
The formula mass for this compound is computed as 58.44 amu (Figure 3.6.3 3.6. Similar to atoms, 1 mole of any compound contains the same number of molecules as 1 mole of any other compund. Sodium chloride is an ionic compound composed of sodium cations, Na +, and chloride anions, Cl, combined in a 1:1 ratio.