PS7_08-Solution

# PS7_08-Solution - Chem 444B Homework Set #7 - Solutions...

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Problem Set #7 -1- Chem 444B Homework Set #7 - Solutions DUE: Friday, March 14, 2008 1) The partial molar volumes of acetone (M M =58.08 g/mol) and chloroform (CHCl 3 , M M =119.37 g/mol) in a mixture in which the mole fraction of CHCl 3 is 0.4693 are 74.166 cm 3 /mol and 80.235 cm 3 /mol, respectively. What is the volume of a solution of mass 1.000 kg? Note: There are a number of valid ways to solve this problem. This is just one example… The total volume of the solution is given by Eq. 24.7, We know the partial molar volumes, but we need to solve for the number of moles of each Set up a series of equations. .. 1) AA CC C C AC VV n V n n x nn =+ = + () 2) Use molar masses to express the total mass: 1 A CA C C t o t AA CC CA C C A A t o t C x xn n n m nM nM xn n x nx nM m n += = + ⎛⎞ ⎜⎟ =− = = ⎝⎠ ±²²³ C 1 Now set these two expressions equal and solve for n : 1 119.37 0.5307 0.4693 58.08 C t o t C C tot C C Ct o t A C A C M m n M xM mn M Mm x n M g mol n g m == + ( ) 33 3 1000 58.08 5.40 5.40 0.5307 6.11 0.4693 74.166 6.11 80.235 5.40 886.8 C A C g g ol mol nm o l mol o l x cm cm V V n V n mol mol cm mol mol = = = =+= + =

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Problem Set #7 -2- 2) (McQ&S, 24-19) These two molecules form ideal solutions so we can readily calculate the vapor pressure of the system. * 1 * 2 214 torr (tetrachloromethane) 138 torr (trichloroethylene) P P = = ** * * * 11 2 2 1 2 2 1 2 () 214 (76) in torr total total Px P x P P x P P =+= + =− * 22 2 12 2 * 21 ; total total P PP P y x P P =+ = = +− solve for x 2 in terms of y 2 and substitute in the first expression for P total : * * 22 2 1 * 2 * * * 1 * * 2 214 138 in torr 138 (76) total total total yP yx P P xP x Py P P P P y = = −− = = + Vapor Pressure 135 145 155 165 175 185 195 205 215 225 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Mole Fraction X2 y2
Problem Set #7 -3- 3) (McQ&S, 24-50) Make a plot of vapor pressure vs. mole fraction of ethanol for both ethanol and water: Vapor pressure vs mole fraction of ethanol 0.00 10.00 20.00 30.00 40.00 50.00 60.00 0.20 0.40 0.60 0.80 1.00 Mole fraction of ethanol Vapor pressure (torr) Ethanol Water Henry’s law constant for a component is the slope of the curve near the point where the mole fraction of that component approaches 1.

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## This homework help was uploaded on 04/13/2008 for the course CHEM 444 taught by Professor Jameslis during the Spring '08 term at University of Illinois at Urbana–Champaign.

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PS7_08-Solution - Chem 444B Homework Set #7 - Solutions...

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