This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: ChemE 178 HW7 Due Oct31 1.) The following osmotic pressure data was obtained for polystyrene in toluene at 25 C. Concentration (g/cm 3 x 10 3 ) (cm toluene) 2.56 0.325 3.8 0.545 5.38 0.893 7.8 1.578 8.86 1.856 The density of toluene is 0.8618g/cm 3 and g=981 cm/s 2 . a) Calculate the number average molecular weight. Osmotic pressure can be related to molecular weight and the second virial coefficient by: c A M RTc n 2 1 + = To find M n , plot /RTc vs c. The y-intercept of the plot is 1/M n . In order to make the plot, put all of the data into a consistent set of units. I used MKS (meter, kilogram, second units), but CGS (centimeter, gram, second units) is also good. Pressure expressed in terms of centimeters of Toluene is a rather ungainly unit. It is better to convert it to Pascals immediately . So convert concentration to kg/m 3 and convert osmotic pressure to Pa: C (g/cm 3 x 10-3 ) (cm toluene) (Pa) C (kg/m 3 ) 2.56 0.325 27.47634 2.56 3.8 0.545 46.07571 3.8 5.38 0.893 75.49652 5.38 7.8 1.578 133.4082 7.8 8.86 1.856 156.911 8.86 Now calculate gh...
View Full Document
This note was uploaded on 12/09/2011 for the course CHEM ENG 178 taught by Professor Segalman during the Fall '08 term at University of California, Berkeley.
- Fall '08