Monday 1 May 2017

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 ]


Answer:

The formula of carbon dioxide = CO2

Relative molecular mass of CO2 = 1 x 12 + 2 x 16 = 44


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