325075
If \(\mathrm{N}_{1}, \mathrm{~N}_{2}, \mathrm{~N}_{3}\) are the number of molecules with molecular masses\({{\rm{M}}_{\rm{1}}}{\rm{,}}\,{{\rm{M}}_{\rm{2}}}{\rm{,}}\,{{\rm{M}}_{\rm{3}}}\) respectively, then mass average molecular weight is
Mass average molecular mass \({\text{ = }}\frac{{\sum {{{\text{N}}_{\text{i}}}} {\text{M}}_{\text{i}}^{\text{2}}}}{{\sum {{{\text{N}}_{\text{i}}}} {{\text{M}}_{\text{i}}}}}\) where \({{\text{N}}_{\text{1}}}{\text{,}}{{\text{N}}_{\text{2}}}{\text{,}}{{\text{N}}_{\text{3}}}\) are the number of molecules with molecular masses \({{\text{M}}_{\text{1}}}{\text{,}}{{\text{M}}_{\text{2}}}{\text{,}}{{\text{M}}_{\text{3}}}\) respectively.