7. The following data were obtained by membrane osmometry of solutions of a polyethylene sample in xylene at 90°C. At this temperature the density of xylene is 0.8014 and that of polyethylene is 0.8173. Calculate the molecular weight of the sample and the second virial coefficient.
c (g/liter): 2.00 4.00 6.00 8.00
π (cm xylene): 2.585 5.965 9.660 13.935
8. A polymer with M = 100,000 obeys the Mark-Houwink equation with K = 1 x 10^-4 and a = 0.80 Huggins' constants is 0.33. Calculate the relative viscosity at c = 0.30 g/dl.