ECHE 311/SPRING 2015
Quiz 5
1. Given x1=0.6, Psat=87.17 kPa, P=70 kPa , using Raoult’s law calculate y1.
2.
10 points
Figure 12.5, ( represent the Pxy data at 50oC for methyl ethyl ketone(1)/toluene(2) and
the liquid-phase properties from VLE data for methyl ethyl ketone(1)/toluene(2) at 50oC,
respectively.
The
ln  i vs xi plots were obtained using the Eq (1) which is valid for low pressure
VLE.
i 
The values of
yi P
xi Pi
(1)
sat
G E / RT
were calculated by:
G E / RT  xi ln  1  x2 ln  2
The values of
G E / RT
so calculated were divided by
G E / x x RT
x1 x 2 to provide in
addition values of
. All these functions are properties of liquid
1 2
phase. Fig. 12.5 shows how each varies with composition.
1
Evaluate the following:
a)
b)
c)
lim  i
10 points
xi 1
GE
lim
xi 0 RT
lim
15 points
GE
15 points
xi 0 x x RT
1 2
2
3. The Margules equations can be written in the form:
ln  1  x22 [ A12  2( A21  A12 ) x1 ]
and
ln  2  x12 [ A21  2( A12  A21 ) x2 ]
Determine from Fig. 12.5 the values of
infinite dilution.
A12 and A21 for the limiting condition of
20 points
3
4) Using a modified Raoult’s law
i 
yi P
xi Pi
sat
show how Eqs. 2 and 3 were obtained
for binary system:
15 points
P  x1 1P1sat  x2 2 P2sat
y1 
x1 1P1sat
x1 1P1sat
 x2 2 P2sat
4
(2)
(3)
5) Show how one can calculate
P and y1
at various values of
5
x1 .
15 points