HW_wk10_solutions_2006

# HW_wk10_solutions_2006 - 2R03 HW for weeks 10 Nov 2006...

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2R03 HW for weeks 10 Nov 2006 STUDENT NAME ______________ _____________ STUDENT NUMBER ___________ Credit: 1.5% if submitted with fully explained solutions on or before the due date of Nov 29, 2006 ( drop boxes ##28-30 , which are located in ABB 1 st floor in the beginning of the hallway behind the blue doors opposite the main office ABB-156). Please attend the assigned tutorials if you have any question on these exercises . Note: All gases are assumed to be ideal and all thermochemical data are for 298.15K unless otherwise specified 1 The osmotic pressure of an aqueous solution of urea at 300K is 120 kPa. Calculate the freezing point of the same solution. Solution: We have [ ] [ ] f urea urea urea f f urea f f water water water K b n b V T K b K K m m ρ ∆ = = = and we can obtain [ ] urea b from the expression of osmotic pressure [ ] urea b RT o = so combining these two equations : 1 1 1 3 [ ] (1.86 )(120 ) 0.089 (8.315 )(300 )(1000 ) f urea f f water water K b K Kkgmol kPa T K RT JK mol k kgm - - - - ∆ = = = = Therefore, assuming water freeze at 0 o C we have that the solution will freeze at about 0.089 o C - . 2. A mixture of 50 g (0.59 mol) of hexane and 100 g (0.82 mol) of nitrobenzene was prepared at 1 atm and 273 K (< the upper critical solution temperature which is 290K at 1 atm). What are the compositions of the phases and in what proportions do they occur knowing that the line T=273K intersects the 1phase/2phases boundary at molar fractions of nitrobenzene of 0.09 and 0.95?

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HW_wk10_solutions_2006 - 2R03 HW for weeks 10 Nov 2006...

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