页数：51页文件大小：4.08 MB来源： Atkins’PhysChem物理化学ppt课件
本课件进入相图：先给出相、组分、自由度与相律等术语，再读单组分相图，随后分析二组分液-气平衡的温度-组成图，讨论蒸馏分离、共沸混合物与杠杆规则的具体用法。
Phase Transformations Phases, Components and Degrees of Freedom Two - Component Syst
相图
Phases, Components and Degrees of Freedom Phase diagrams are extremely useful for systems with multiple components, and serve to describe physical and chemical equilibria over a range of different compositions, as well as points where substances are mutually miscible, or even when a system has to be brought to a specific set of conditions for equilibrium to exist (e.
g., pressure, temperature and composition)
相图
Phases, Components and Degrees of Freedom All phase diagrams are developed around one relationship, the phase rule (相律), which was derived by J. W. Gibbs - it can be applied to a wide variety of systems. Phase diagrams: pictorial way of understanding the properties of a system
8.1 Some Definitions Phase: Signifies a form of matter that is uniform throughout, not only in chemical composit
8.1 Some Definitions is denoted by P: P = 2 for slurry of ice and water, immiscible metal alloys Number o
8.1 Some Definitions is denoted by P: A dispersion (example b) is uniform macroscopically, but not on the
8.1 Some Definitions A chemical species that is present in a system. For example, a mixture of water and
8.1 Some Definitions
Components Example Consider the thermal decomposition of N H 4 Cl
Components Example C = 3 － 1 － 0 = 2
Components Example If additional HCl or N H 3 were added to the system, decomposition of the N H 4 Cl w
Components Example At room temperature, O 2 (g) and H 2 (g) do not react to form water, so they are not
Variance and Degrees of Freedom is the number of intensive variables in a system that can be changed independently w
Variance and Degrees of Freedom In a single - component, single - phase system (C = 1, P = 1) the pressure and tempe
Variance and Degrees of Freedom If two phases are in equilibrium in a single - component system (C = 1, P = 2) (e. g
8.2 The phase rule (相律) J. W. Gibbs, regarded as America’ s first theoretical scientist and the father of ch
(a) One component systems For C = 1, F = 3 – P: P = 2, F = 1 P = 3, F = 0 P ≠ 4 when C = 1 since F ≥ 0 P ≠ 4 w
Phases, Components and Degrees of Freedom a. P = 1 F’ = 1 at constp Consider pure water: b. P = 2 F’ = 0 atTbandconstpc. P = 1
Phases, Components and Degrees of Freedom
Phases, Components and Degrees of Freedom The difference between triple point and ice point of H 2 O 纯水冰三相点冰点被空气饱和的水冰水蒸气p = 61
(b) Experimental Procedures Thermal analysis: Detecting phase transitions is tricky, requiring special technique
(b) Experimental Procedures Cooling curve for the isobar cdein the water phase diagram is: 步冷曲线
(b) Experimental Procedures High pressure phase transitions can be observed in the diamond - anvil cell, in whic
Two Component Systems When there are two components in a system, C = 2, and F = 4 - P, so if the temperatu
8.3 Vapour pressure diagrams Partial p of components of an ideal solution of two volatile liquids are related to
(a) The composition of the Vapour Compositions of liquid and vapour in equilibrium are not necessarily the same, vapou
(a) The composition of the Vapour In all cases, y A > x A (vapour richer in more volatile component). If B is non - vo
(a) The composition of the Vapour The total vapour pressure as composition of the vapour: p A * / p B *
(b) Interpretations of the Diagrams For distillation s, both vapour and liquid contributions are of interest, so we comb
(b) Interpretations of the Diagrams The horizontal axis shows the overall composition, z A, of the system a: only a liqu
(b) Interpretations of the Diagrams a 1: Liquid is in eqm with its vapour (composition of vapour phase given by a 1’ a 2
(b) The Lever Rule (杠杆规则) The point in a two - phase region indicates not only qualitatively, but also quantit
(b) The Lever Rule (杠杆规则)
8.4 Temperature Composition Diagrams T - x diagrams show the boundaries of compns of phases at eqm at different temperatu
(a) The distillation of mixtures a 1: pure phase liquid is heated and boilsatT 2, with composition a 2 = a 1, vapour
(a) The distillation of mixtures Simple distillation Fractional distillation Theoretical plates
(a) The distillation of mixtures x 50.00. 20.40. 60.81. 0 lgC 6 H 5 CH 3 (A) C 6 H 6 (B) xBt / ℃ 1401208010060 y 5 y
(a) The distillation of mixtures
(a) The distillation of mixtures 现代化炼油厂的精馏塔
(b) Azeotrope s High - Boiling Azeotrope s Sometimes favourable interactions between molecules reduc
(b) Azeotrope s
(b) Azeotrope s Low Boiling Azeotrope s The diagram right also shows azeotropic behaviour, except th
(b) Azeotrope s Low Boiling Azeotrope s
(c) Immiscible Liquids Distillation of two immiscible liquids A and B (example, octane and water) and at eq
(c) Immiscible Liquids The total vapour pressure is close top = p A * + p B * If p = atmospheric pressure,
Exercises (a) 8.4, 6,9, 12 (Discussion: Exercises 8.2 a) Homework
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