SOLUTION TO HOMEWORK #7
10.1-1
a.
In order to solve this problem, we need to know what happens at the bubble point;
at this point, the first bubble is formed, so we can assume that all of the number of
moles for the components in the gas phase are close to zero (yet there is an
equilibrium). Therefore, we use the compositions given in the problem statement
and we assume they are the compositions of the liquid. (x=z, z being the
composition given).
x
ET
=
0.05
x
P
=
0.10
x
NB
=
0.40
x
MP
=
0.45
Now, we know, from Raoult’s law that:
y
i
=
x
i
P
i
vap
P
and from the problem statement we know that the pressure is 5 bar. Therefore, we
proceed to calculate the bubble point temperature. The way the bubble point temperature
is done is by doing the following. We also
know that:
y
i
i
∑
=
1
and therefore, substituting
1
vap
i
i
i
i
i
x P
y
P
=
=
∑
∑
Therefore:
1
=
x
ET
P
ET
vap
+
x
P
P
P
vap
+
x
NB
P
NB
vap
+
x
MP
P
MP
vap
P
Now, we do the following:
1
=
x
ET
10
−
A
T
(
)
+
B
⎡
⎣
⎢
⎤
⎦
⎥
ET
+
x
P
10
−
A
T
(
)
+
B
⎡
⎣
⎢
⎤
⎦
⎥
P
+
x
NB
10
−
A
T
(
)
+
B
⎡
⎣
⎢
⎤
⎦
⎥
NB
+
x
MP
10
−
A
T
(
)
+
B
⎡
⎣
⎢
⎤
⎦
⎥
MP
P

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