Polymers: Molecular weight definition?

Question

What is the difference between number average molecular weight and weight average moecular weight?

Answer 1

The number average molecular weight is a way of determining the molecular weight of a polymer. Polymer molecules, even ones of the same type, come in different sizes (chain lengths, for linear polymers), so the average molecular weight will depend on the method of averaging. The number average molecular weight is the common average of the molecular weights of the individual polymers. It is determined by measuring the molecular weight of n polymer molecules, summing the weights, and dividing by n.

The weight average molecular weight is a way of describing the molecular weight of a polymer. Polymer molecules, even if of the same type, come in different sizes (chain lengths, for linear polymers), so we have to take an average of some kind. For the weight average molecular weight, this is calculated by
M_n=frac{sum_i N_iM_i^2}{sum_i N_iM_i}

where N_i is the number of molecules of molecular weight M_i.

Answer 2

I believe the first refers to the number of atoms (usually carbon atoms) in the polymer chain, and the other refers to the molecular weight of the chain

either value will indicate polymer length

Answer 3

Yes you're taking the sum of the loads of the elemnts of the molecule. Do no longer omit to multiply each and every mass of atom by means of their quantity within the molecule Ex H2SO4 in a periodic desk you uncover atomic mass H= a million , S= 32 O =sixteen So molecular mass a million*two + 32 + sixteen*four = ninety eight g