the properties of mixtures
DESCRIPTION
The properties of mixtures. 자연과학대학 화학과 박영동 교수. 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 6.1.5 Real solutions: activities - PowerPoint PPT PresentationTRANSCRIPT
The properties of mixtures
자연과학대학 화학과박영동 교수
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 6.1.5 Real solutions: activities
6.2 Colligative properties
6.2.6 The modification of boiling and freezing points 6.2.7 Osmosis
6.3 Phase diagrams of mixtures
6.3.8 Mixtures of volatile liquids 6.3.9 Liquid-liquid phase diagrams 6.3.10 Liquid-solid phase diagrams 6.3.11 The Nernst distribution law
=
The partial molar volumes ofwater and ethanol at 25°C.
partial molar volume
At 25°C, the density of a 50 per cent by mass ethanol/water solution is 0.914 g cm-3. Given that the partial molar volume of water in the solution is 17.4 cm3 mol-1, what is the partial molar vol-ume of the ethanol?
partial molar Gibbs energy, GJ
Pressure dependence of G
ch05f01
G = H – TSdG = dH – TdS – SdT = Vdp - SdT
= V
For liquid or solid, ΔG = VΔp
For vapor, ΔG = ∫Vdp = nRT ∫(1/p)dp=nRT ln(pf/pi)
ΔGm = RT ln(pf/pi)
Chap. 5
The Gibbs energy of mixing of two perfect gases of two liquids that form an ideal solution.
Chap. 4The entropy change with isothermal expansion
ch04f04
2
12 2 2
1 1 1
2 2
1 1
1
1
ln ln
S dqT
p nRdw dV dVT T V
V pnR nRV p
The entropy of mixing of two perfect gases of two liquids that form an ideal solution.
Raoult's law:
pA =xApA*
Figure 6.6 The partial vapour pressures of the two components of an ideal binary mix-ture are proportional to the mole fractions of the components in the liquid. The total pres-sure of the vapour is the sum of the two par-tial vapour pressures.
The partial vapour pres-sure of a substance in a liquid mixture is propor-tional to its mole fraction in the mixture and its vapour pressure when pure:
Raoult’s law
CS2 is more volatile
certain composition makes the solution more volatile
Figure 6.6 The partial vapour pressures of the two components of an ideal binary mix-ture are proportional to the mole fractions of the components in the liquid. The total pres-sure of the vapour is the sum of the two par-tial vapour pressures.
The partial vapour pres-sure of a substance in a liquid mixture is propor-tional to its mole fraction in the mixture and its vapour pressure when pure:
Raoult’s law: for Ideal solution, esp. for solvent
chemical potential of a solvent A present in solution at a mole fraction xA is
At equilibrium, chemical potential of any given component is same every-where.
Henry’s law, for ideal solutes
The experimental partial vapour pressures of a mixture of trichloromethane, CHCl3 (C), and propanone, CH3COCH3 (acetone, A),
The chemical potential of the solute has its standard value when the molar con-centration of the solute is 1 mol dm−3 (that is, ).
G = H – TSdG = dH – TdS – SdT = Vdp – SdTdμ = Vmdp – SmdT
μ*
μ*+ RT ln xA
-Sm(s)ΔT
-Sm(l)ΔT RT ln xA
{Sm(l) - Sm(s) }ΔT = RT ln xA
μs = μ*– Sm(s) dT
μl = μ*– Sm(l) dT + RT ln xA
μ*+ RT ln xA
μ*
Sm(g)ΔT
Sm(l)ΔT
{Sm(l) - Sm(g) }ΔT = RT ln xA
{Sm(l) - Sm(g) }ΔT = RT ln xA
μg = μ*– Sm(g) dT
μl = μ*– Sm(l) dT + RT ln xA
μA(xA=1, p) μA(xA, p+Π)μA(xA=1, p) = μA(xA, p+Π)
pA = xA pA *= a pA
*
pB = xB pB * = (1-a) pB
*
a'= pA /(pA + pB) = a pA * /(a pA
* + (1-a) pB
*)
= a pA * /(pB
* + a(pA *- pB
* ))
Understanding fractional distilla-tion
a'= pA /(pA + pB)
= a pA * /(a pA
* + (1-a) pB
*)
= a pA * /(pB
* + a(pA *- pB
* ))
a'= aX/(1+a(X-1))
where X = (pA * / pB
*)
a'= yA = mole fraction in vapor
a= xA = mole fraction in liquid
Liquid-Vapor Composition and fractional distillation
A: more volatile substance
B: less volatile substance나오는 것은 A, 남는 것은 B
lever rule and phase diagram
low-boiling(positive) azeotrope
repeated distillation can never pro-duce a distillate that is richer in con-stituent X than the azeotrope
끓어 나오는 것은 Azeotrope, 남는 것은 A 나
B
high-boiling(negative) azeotrope공비 ( 共沸 ) 혼합물
끓어 나오는 것은 A 나 B이지만 , 남은 것은 Azeotrope