# Relative Molecular Mass

The relative molecular mass (Mr) of an element is the average mass of one molecule of the element/compound when compared with   of the mass of an atom of carbon-12, which taken as 12 units.

The relative molecular mass of a molecule is equal to the sum of the relative atomic mass of all the atoms in the molecule.

Example
Find the relative molecular mass of carbon dioxide.
[ JAR: C = 12; O = 16 ]
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