Number-, Mass- and Z-Average Molar Masses

The first quantity is a colHgative property called the number-average relative molar mass or simply the number-average molar mass denoted M and defined as the weighed average of the number fraction of each macromolecule by the following equation. 

Because the number-average molar mass is a colligative property, it can be determined experimentally by techniques which are able to count the number of macromolecules such as osmotic pressure measurements. 

The mass-average molar mass is determined by optical methods such as Rayleigh light scattering measurements. 

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