Subjective questions Question 1
a. A solution is prepared by dissolving 0.432 g of polymer of unknown structure in 140
mL of hexane. Vapor pressure of pure hexane at 30.5 kPa meanwhile the vapor
pressure of the solution at 40°C was found to decrease by 12% of that pure hexane.
Density of hexane is 659 kg/m².
i. Calculate the mole fraction (X) of the polymer in the solution.
ii.
Calculate the molar mass of the polymer.
If the solute is replaced with a same number of moles of toluene (a volatile
compound), explain the effect on the vapor pressure of the solution based on
Roult's law.

3. consider a process in which a gas with the properties of air expands at constant pressure as described by the cups of air discussion in class. one kilogram of air starts out at 1 atm and 290 k. the air expands its volume by absorbing a sufficient amount of thermal energy to increase the temperature at constant pressure to 350 k. a. on a p-v diagram, sketch this process with point a as the starting point and point b as the ending point. b. if the process is completely reversible, calculate the thermal energy added from an external source. c. calculate the entropy change for this process assuming it is reversible. d. calculate the work delivered externally if this is a reversible process. e. if the process is completely irreversible, calculate the amount of entropy change for the process that is due to irreversibilities. f. if the process is completely irreversible, calculate the amount of thermal energy added from an external source and compare this result to the thermal energy calculated in part b. g. for the completely irreversible process, calculate the entropy change due to this thermal energy addition. h. for the completely irreversible process, calculate the total entropy change and compare it to the entropy change in part c.