Polyisobutylene (PIB) is equilibrated in propane vapor at 35 oC. At this temperature, the saturated pressure (p10) of propane is 9050 mm Hg and its density is 0.490 g/cm3. PIB has a molecular weight of approximately one million and a density of 0.915 g/cm3. The concentration of propane, c, sorbed by PIB at different partial pressure of propane (p1) is given in the following table. Using this information, determine tan average value of the Flory interaction-parameter, ?12, for the PIB-propane system P1 (mm Hg) c (g propane / g PIB) 496 0.0061 941 0.0116 1446 0.0185 1452 0.0183 [Treat the PIB vapor as ideal gas. Note the difference between c & ?]