number-average molar mass

symbol: $M_{\rm{n}}$; units: $\pu{g mol-1}$, $\pu{kg mol-1}$
https://doi.org/10.1351/goldbook.12216
The equation for number-average molar mass is \[M_{\rm{n}} = \frac{1}{\sum\limits_{M} (w_{M}/M)}\] The equation for number-average molecular weight is \[M_{\rm{r,n}} = \frac{1}{\sum\limits_{M_{\rm{r}}}(w_{M_{\rm{r}}}/M_{\rm{r}})}\]
Notes:
  1. For definition of the symbols, see molar-mass average.
  2. Quantities number-average molecular weight, number-average relative molar mass, and number-average relative molecular mass (\(M_{\rm{r,n}}\)) are synonyms. These quantities are dimensionless (pure numbers) and are not associated with any units.
Source:
PAC, 2015, 87, 71. (Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)) on page 83 [Terms] [Paper]
Citation: 'number-average molar mass' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.12216 RIS BibTex EndNote
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