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Subject: Azeotrope for the chloroformmethanol system at 101.3 kPa.
Given: Vaporliquid equilibrium data from Section 13, p. 11 of Perry's Handbook, 6th edition.
Find: From data, construct yx and Txy plots. Azeotrope conditions
Analysis: See plots below. From these plots, a minimumboiling azeotrope occurs at 53.5oC
with a composition of 65 mol% chloroform and 35 mol% methanol. Exercise 4.14
Subject: Azeotrope for the waterformic acid system at 101.3 kPa.
Given: Vaporliquid equilibrium data from Section 13, p. 14 of Perry's Handbook, 6th edition.
Find: From data, construct yx and Txy plots. Azeotrope conditions
Analysis: See plots below. From these plots, a maximumboiling azeotrope occurs at 107.6oC
with a composition of 42 mol% water and 58 mol% formic acid. Exercise 4.15
Subject: Partial vaporization of a water (A) isopropanol (B) mixture at 1 atm.
Given: Vaporliquid equilibrium data at 1 atm and vaporpressure data.
Find: (a)
(b)
(c)
(d)
(e) Construct Txy and yx diagrams.
Composition of vapor when a 60 mol% A  40 mol% B mixture is at its bubble point.
Composition of vapor and liquid for 75 mol% vaporization of mixture in Part (a).
Kvalues and αvalues at 80 and 89oC.
Comparison of parts (a), (b), and (c) to results from using Raoult's and Dalton's laws. Analysis: (a) The following are plots of the given equilibrium data, including the purecomponent normal boiling points. Exercise 4.15 (continued)
Analysis: (a) continued Exercise 4.15 (continued)
Analysis:
(b) From the yx plot on the previous page, the composition of the first bubble of
vapor is 57 mol% isopropanol and 43 mol% water. See the qline on the diagram.
(c) For 75 mol% vaporization, use the inverse leverarm rule on the Txy
diagram or plot a qline on the yx diagram. For the latter, from the equation above Eq. (46),
the slope of the qline is [(V/F)1]/(V/F) = (0.751.0)/0.75 = 0.333. The construction is shown
on the yx diagram, where the intersection with the equilibrium curve gives xA = 0.14 and yA =
0.50.
(d) Can not compute the Kvalues or α at 80oC, because this temperature is below
the lowest boiling mixture, which is the azeotrope.
At 89oC, the Txy diagram gives the following compositions from the line shown on the
above diagram:
yB = 0.35, yA = 0.65
xB = 0.035, xA = 0.965
From Eq. (219) for the definition of the K value,
KB = yB 0.35
=
= 10
xB 0.035 KA = yA
0.65
=
= 0.67
xA 0.965 From Eq. (221) for the definition of the relative volatility, α, noting that at 89oC and 1 atm,
isopropanol is more volatile,
K
10
α B,A = B =
= 15
KA 0.67
(e) To calculate Txy curves from vapor pressure data, using Raoult's and
Dalton's laws, Eq. (244 ) applies, as well as the sum of the mole fractions in the phases in
equilibrium. Thus,
s
s
yA PA T
yB PB T
KA =
=
,
KB =
=
(1, 2)
xA
P
xB
P
yA + y B = 1 , xA + x B = 1 (3, 4) Equations (1) to (4) can be reduced to the following equations for the mole
fractions of benzene in terms of the Kvalues:
1 − KB
,
y A = KA x A
(5, 6)
KA − KB
If...
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 Spring '11
 Levicky
 The Land

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