Misturas Simples e Pressão

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146 5 SIMPLEMIXTURES
�e abundance of the two phases is therefore equal.
P5C.8 �e relationship between the total pressure p and yA is given in [5C.5–167]
p = p∗Ap
∗
B
p∗A + (p∗B − p∗A)yA
Division by p∗A, and then division of the numerator and denominator of the
fraction on the right by p∗B gives the required form
p
p∗A
= p∗B
p∗A + (p∗B − p∗A)yA
= 1
(p∗A/p∗B) + (1 − p∗A/p∗B)yA
�e plot is shown in Fig. 5.15.
0.0 0.2 0.4 0.6 0.8 1.0
0.0
0.2
0.4
0.6
0.8
1.0
yA
p/
p∗ A
(p∗A/p∗B) = 2
(p∗A/p∗B) = 4
(p∗A/p∗B) = 30
Figure 5.15
P5C.10 �e values of xA at which ∆mixG is a minimum are found by solving [5C.7–174]
ln xA
1 − xA
+ ξ(1 − 2xA) = 0 (5.6)
�is equation is rearranged to give an expression for ξ, which is plotted in
Fig. 5.16
ξ = ln(xA/[1 − xA])
2xA − 1
�e way to interpret this graph is to choose a value for ξ and then read across to
locate the minima. If ξ 2 there are two values of xA at which the plotted
function intersects a horizontal line at a given value of ξ.�e larger ξ becomes
the close one intersection (position of a minimum) moves towards xA = 0 and
the other towards xA = 1.