Molar Mass
(Molecular Weight)

Molecular compounds consist of a large collection of molecules. The molar mass (or molecular weight) of a molecular compound is defined in the following way:

Molar Mass = Mass of 1 mole of molecules

Therefore, to get the molar mass of a molecular compound we need simply determine the molar mass of molecules. For sucrose (table sugar) we have the molecular formula C12H22O11 and the molar mass would be

Molar mass of sucrose

= 12x12.011 g + 22x31.008 g + 11x15.999g

= 342.3 g

Or, we would say that the molar mass of sucrose = 342.3 g/mol (i.e., a mole of sucrose molecules has a mass of 342.3 g)

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C101 Class Notes
Prof. N. De Leon