In a polymer sample, 30% of molecules have a molecular mass 20000, 40% have 30000 and the rest have 60000. What is the weight average molecular mass of the polymer? (Kerala CEE 2006)

The polymer contains 30% molecules of mass 2000, 40% molecules of molecules mass 30000 and rest 30% molecules of molecular mass 60000. Thus, 2 2 2 2 w 30 20000 40 30000 30 60000 M 30 20000 40 30000 30 60000 i i i i N M N M x x x w M 43333