Just as with elements, stoichiometry of compounds requires converting between mass (grams) and amount (moles). The key concepts are:

• 1 The molar mass of a compound is the sum of the atomic masses of all atoms in one formula unit, measured in g/mol.
• 2 One mole of any compound contains 6.022 × 10²³ formula units.
• 3 To convert grams → moles: divide by molar mass.   n = m ÷ M
• 4 To convert moles → grams: multiply by molar mass.   m = n × M

Molar Masses of Common Compounds

Use this table as a reference. Practice until you no longer need it.

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