Molar Mass of a Compound

Calculate the molar mass of a molecule or formula unit by summing the molar masses of its constituent atoms, each weighted by how many appear.

$$M_{\text{compound}}=\sum _i{k}_i{M}_i$$

Variables

Symbol	Meaning	Unit
$M_{\text{compound}}$	Molar mass of the compound	g/mol
$k_i$	Number of atoms of element i in the formula	count
$M_i$	Molar mass of element i	g/mol

Worked example

Water: [2 x 1.008] + [1 x 15.999] = 18.015 g/mol. Sodium chloride: 22.99 + 35.45 = 58.44 g/mol, so 0.141 mol gives 0.141 x 58.44 = 8.24 grams of NaCl.

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Part of The Blueprint of Water