because of this molecular weights are usually given as averages. two experimentally determined values are common: \(m_n\) the number average molecular weight is calculated from the mole fraction distribution of different sized molecules in a sample and \(m_w\) the weight average molecular weight is calculated from the weight
the weight average molecular weight mw. the weight average is a little more complicated. it's based on the fact that a bigger molecule contains more of the total mass of the sample than the smaller molecules do. demographics. a good way to understand the difference between the number average molecular weight and the weight average
molecular weight is the molecular mass of a chain. it can be obtained by multiplying the mass of each repeating unit (m 0) by the degree of isation and then adding the mass of end groups. for a linear it is rare that all chains have the same mass. there is always a distribution existed.
in linear s the individual chains rarely have exactly the same degree of ization and molar mass and there is always a distribution around an average value.the molar mass distribution (or molecular weight distribution) describes the relationship between the number of moles of each species (n i) and the molar mass (m i) of that species.
molecular weight (mw) is the molecular mass of a chain. while small molecules of the same elemental composition all exhibit the same molecular weight chains exhibit different characteristics.