Homework |
Chemistry 595 |
Spring 2008 |
Professor Dadmun |
| Assignment #1 | Due Thur. Feb. 14 |
1.) A polymer is fractionated and found to have the molecular weight distribution shown below. Calculate the number average and weight average molecular weights for this distribution
2.) The following are the measured diameters of a series of spheres:
Number of Spheres |
Diameter (cm) |
2 |
1 |
3 |
2 |
4 |
3 |
2 |
4 |
Calculate the number average (Dn) and weight average (Dw)
diameter of this collection of spheres.
3.) The following osmotic pressure data are available for a polymer solution:
conc (g/dL) |
h (cm of solvent) |
0.32 |
0.70 |
0.66 |
1.82 |
1.00 |
3.10 |
1.4 |
5.44 |
1.90 |
9.3 |
The temperature is 25 °C and the solvent density is 0.85 g/ml. Determine the molecular weight and second Virial coefficient of this polymer solution.
4.) The following Viscosity Data was obtained for polystyrene in toluene at 30 °C
conc (g/dL) |
t (sec) |
0 |
65.8 |
0.54 |
101.2 |
1.08 |
144.3 |
1.62 |
194.6 |
2.16 |
257 |
Determine the value of the Huggins constant, kH, the intrinsic viscosity of the sample and the viscosity average molecular weight of the polymer. You should be able to find K and a for this polymer pair fairly easily.
5.) Given a Size exclusion Chromatography curve that has been calibrated to provide weight of component with molecular weight Mi vs Mi, show explicitly how to determine the number average and weight average molecular weight of the sample from this data.
6.) The data in the table below give Kc/R(q) for polystyrene in benzene. Construct a Zimm plot and calculate the weight average molecular weight of this polymer. What other information on this polymer can you extract from this plot? Determine any additional parameters possible.
