Report

The properties of mixtures 자연과학대학 화학과 박영동 교수 Chapter 6 The properties of mixtures 6.1 The thermodynamic description of mixtures 6.1.1 6.1.2 6.1.3 6.1.4 6.1.5 Partial molar properties Spontaneous mixing Ideal solutions Ideal dilute solutions 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 of water 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 volume of the ethanol? partial molar Gibbs energy, GJ Chap. 5 Pressure dependence of G G = H – TS dG = 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) ch05f01 The Gibbs energy of mixing of two perfect gases of two liquids that form an ideal solution. Chap. 4 The entropy change with isothermal expansion S 1 2 dq T 1 2 1 2 p ch04f04 1 T dV 2 nR V V p nR ln 2 nR ln 2 V1 p1 1 T dw 1 dV The entropy of mixing of two perfect gases of two liquids that form an ideal solution. Raoult's law: pA =xApA* Raoult’s law The partial vapour pressure of a substance in a liquid mixture is proportional to its mole fraction in the mixture and its vapour pressure when pure: Figure 6.6 The partial vapour pressures of the two components of an ideal binary mixture are proportional to the mole fractions of the components in the liquid. The total pressure of the vapour is the sum of the two partial vapour pressures. certain composition makes the solution more volatile CS2 is more volatile Raoult’s law: for Ideal solution, esp. for solvent The partial vapour pressure of a substance in a liquid mixture is proportional to its mole fraction in the mixture and its vapour pressure when pure: Figure 6.6 The partial vapour pressures of the two components of an ideal binary mixture are proportional to the mole fractions of the components in the liquid. The total pressure of the vapour is the sum of the two partial vapour pressures. 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 everywhere. 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 concentration of the solute is 1 mol dm−3 (that is, ). G = H – TS dG = dH – TdS – SdT = Vdp – SdT dμ = Vmdp – SmdT μs = μ*– Sm(s) dT μl = μ*– Sm(l) dT + RT ln xA {Sm(l) - Sm(s) }ΔT = RT ln xA -Sm(s)ΔT -Sm(l)ΔT μ* RT ln xA μ*+ RT ln xA μg = μ*– Sm(g) dT μl = μ*– Sm(l) dT + RT ln xA μ* {Sm(l) - Sm(g) }ΔT = RT ln xA {Sm(l) - Sm(g) }ΔT = RT ln xA Sm(g)ΔT μ*+ RT ln xA Sm(l)ΔT μA(xA=1, p) μA(xA, p+Π) μA(xA=1, p) = μA(xA, p+Π) Understanding fractional distillation 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 * )) Liquid-Vapor Composition and fractional distillation a'= yA = mole fraction in vapor 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= xA = mole fraction in liquid B: less volatile substance 나오는 것은 A, 남는 것은 B A: more volatile substance lever rule and phase diagram low-boiling(positive) azeotrope repeated distillation can never produce a distillate that is richer in constituent X than the azeotrope 끓어 나오는 것 은 Azeotrope, 남는 것은 A나 B 공비(共沸) 혼합물 high-boiling(negative) azeotrope 끓어 나오는 것은 A나 B이 지만, 남은 것 은 Azeotrope