I make PVP (Mw 58000) solution based on the calculation of its repeating unit. for example: Mw/Molar mass = Repeating unit, (58000/111.11=522). Means 1 M = 522 g =1000 ml,,, So how can i find the Mn valve for it??? Thank you
If you want to calculate the Mn from the Mw value you should know the polydispersity index. The number of repeating units usually calculated by dividing the Mn/molar mass
I agree with Hadeia Mashaqbeh above - you need to know the polydispersity index (on a side note, IUPAC apparently has been encouraging the use of "dispersity" for quite some time now) or the molecular weight-frequency distribution of your polymer.
Assuming that you are working with an actual sample rather than approaching the subject theoretically, I would recommend using an analytical method whose results can be interpreted as number-average MW (Mn), such as NMR spectroscopy (by comparing the integrals of end-group signals with those of the repeat unit signals). I will also recommend the following, rather lovely paper on MW determination: Article Polymer Molecular Weight Analysis by 1H NMR Spectroscopy
Polydispersity index refers to distribution profile of molecular weight in a given polymer. It is Mw/Mn while Mn = summation of MiNi/summation of Ni . Polydispersity index will come to your rescue.