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 ##2830
, which are located in ABB 1
st
floor in the beginning of the hallway behind the blue doors
opposite the main office ABB156).
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?
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '05
 GiuseppeMelacini.
 Physical chemistry, Thermodynamics, pH, Gibbs, reaction mixture

Click to edit the document details