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8/9/2019 06 the Properties of Mixtures
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The properties of mixtures
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Chapter 6 The properties of mixtures
6.1 The thermodynamic description of mixtures
6.1.1 Partial molar properties
6.1.2 Spontaneous mixing
6.1.3 Ideal solutions
6.1.4 Ideal dilute solutions
6.1. !eal solutions" acti#ities
6.2 Colligati#e properties
6.2.6 The modification of $oiling and free%ing points
6.2.& 'smosis
6.3 Phase diagrams of mixtures
6.3.( )ixtures of #olatile li*uids
6.3.+ ,i*uid-li*uid phase diagrams
6.3.1 ,i*uid-solid phase diagrams
6.3.11 The /ernst distri$ution la0
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The partial molar volumes ofwater and ethanol at 25C.
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partial molar volume
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t 2C the density of a per cent $y mass
ethanol50ater solution is .+14 g cm-3. i#en that the
partial molar #olume of 0ater in the solution is 1&.4 cm3mol-1 0hat is the partial molar #olume of the ethanol7
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partial molar Gibbs energy, GJ
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ressure dependen!e of G
chf1
G = H TS
dG = dH TdS SdT = Vdp - SdT
= V
For liquid or solid,G= Vp
For vapor,G= Vdp= nRT(1/p)dp=nRT ln(pf/pi)
Gm= RT ln(pf/pi)
Chap.
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The i$$s energy of mixing of t0o perfect gases of t0o
li*uids that form an ideal solution.
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Chap. 4
The entropy change with isothermal expansion
ch4f4
2
1
2 2 2
1 1 1
2 2
1 1
1
1
ln ln
S dqT
p nRdw dV dV T T V
V pnR nR
V p
=
= = =
= =
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The entropy of mixing of t0o perfect gases of t0o li*uids
that form an ideal solution.
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!aoult8s la0"
p2x
2p29
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Figure 6.6 The partial vapour pressures o the twocomponents o an ideal !inary mixture areproportional to the mole ractions o the componentsin the liquid. The total pressure o the vapour is thesum o the two partial vapour pressures.
The partial #apour pressure of
a su$stance in a li*uid mixture
is proportional to its molefraction in the mixture and its
#apour pressure 0hen pure"
"aoult#s law$for Ideal solution, esp. for solvent
http://ebooks.bfwpub.com/elements5e/sections/figurehttp://ebooks.bfwpub.com/elements5e/sections/figure8/9/2019 06 the Properties of Mixtures
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chemical potential o a solvent % present in solutionat a mole ractionx%is
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t e*uili$rium chemical potential of any
gi#en component is same e#ery0here.
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&enry#s law,for ideal solutes
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The experimental partial vapour pressureso a mixture o trichloromethane, '&'l
('), and propanone, '&''&(acetone,
%),
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The chemical potential of the solute has its
standard #alue 0hen the molar concentration of
the solute is 1 mol dm 3 ;that is
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G = H TS
dG = dH TdS SdT = Vdp SdT
d = Vmdp SmdT
*
*+RTlnxA
-Sm(s)T
-Sm(l)TRTlnxA
{Sm(l) - Sm(s) }T = RTlnxA
s= * Sm(s) dT
l= * Sm(l) dT + RT lnxA
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*+RTlnxA
*
Sm(g)T
Sm(l)T
{Sm(l) - Sm(g) }T = RTlnxA
{Sm(l) - Sm(g) }T = RTlnxA
g= * Sm(g) dT
l= * Sm(l) dT + RT lnxA
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A(xA=1, p) A(xA, p+)A(xA=1, p) =A(xA, p+)
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pA =xApA*=apA
*
pB =xBpB * = (1-a)pB *
a'= pA /(pA +pB) = apA*/(apA
*+(1-a)pB
*) apA
*5;pB*= a;pA
*-pB*
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a'= pA /(pA +pB)= apA
*/(apA*+(1-a)pB
*)
apA *5;pB *= a;pA *-pB *
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low-boiling(positive) azeotrope
repeated distillation can ne#er produce a
distillate that is richer in constituent > than
the a%eotrope
%eotrope
?
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high-boiling(negative) azeotrope ; <
?
%eotrope
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