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物理化学偏摩尔量.ppt

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    • 物理化学物理化学(Ⅰ)PHYSICAL CHEMISTRY (9) 过程方向和限度判据:孤立系统DS,熵增加原理封闭系统DS,熵增加原理绝热过程DA,赫姆霍兹函数减小原理等温无功(等V, W’=0)DG,吉布斯函数减小原理等温等压W’=0?(有物质交换发生)开放系统DS,考虑环境、构建孤立系其它过程 第三章第三章 溶液热力学基础溶液热力学基础Thermodynamics of Multi-component Systems (Solution Chemistry)3.1 Partial molar quantities(偏摩尔量偏摩尔量)1.Characteristics of multi-component and heterogeneous systems(1) Composition and the amounts of substances are changeable in systems involving phase transitions and chemical reactions. (对其中的一相而言,可看作开放系统) Volume Change upon Mixing of C2H5OH(A) and H2O(B)wA% VA*/cm3 VB*/cm3 (VA*+VB*)/cm3 V/cm3 DV/cm3 20 25.34 80.32 105.66 103.24 2.42 40 50.68 60.24 110.92 106.93 3.99 60 76.02 40.16 116.18 112.22 3.96 80 101.36 20.08 121.44 118.56 2.88(2) Nonadditivity of extensive properties, such as volume。

      (3) More than 3 independent variables are needed to define the state of a system.2. Partial molar quantitiesTaking volume as an example. For a system at thermal and mechanical equilibrium, we have Define:as partial molar volume of substance B Partial molar internal energyPartial molar enthalpyPartial molar entropy Partial molar volumes of H2O and CH3CH2OH at 25oC Discussion:① Partial molar quantities are intensive properties of a system. (强度性质)② Perspectives of physical significanceVxB nBChanging rate of V against nB at a given state (T, p, and concentration xB). 偏摩尔体积也可看作是在等温等压等温等压的条件下,在无限大无限大的系统中加入1 mol B所引起系统体积的变化量。

      ③ Conditions: Constant T and p.④ For a mono-component system, 3. Two important equations of partial molar quantities (1) Additivity of partial molar properties (偏摩尔量的偏摩尔量的集合公式,集合公式,或或加和公式加和公式)在指定T,p 均不变的条件下V是nB的一次齐函数根据齐函数的Euler定理即: (2) Gibbs - Duhem equationAt constant T and p,FromBy comparison, we have For binary systems, (A+B),VA是nA的零次齐函数,根据齐函数的Euler定理Or, Problem::集合公式和Gibbs - Duhem 方程的适用条件相同吗?Similarly,We may also have, 4. Determination of partial molar quantities(1) 切线法切线法(2) 解析法解析法如能从实验或理论得到方程 (3) 截距法截距法定义:可以证明:VAVBVmxB0 1 3.2 Chemical potential and fundamental equations of thermodynamics for open system1. Chemical potentialDefine: as chemical potential of component B For closed system , dnB= 0 Set : Define: Fundamental Equations of Chemical Thermodynamics for Open Systems(开放系统的热力学基本关系式开放系统的热力学基本关系式)At a given state, Discussion: ① μB是强度性质, μB= f ( T,p,xB,…) ② 适用条件: 处于热平衡热平衡和力平衡力平衡的,没有非体没有非体积功积功的均相均相系统 AssignmentsReview (XC Fu): 4.1~4.3 Further Reading (PWA): 7.1~7.2Homework: Fu: Chapter 4:1,4 Atkins: Problems 7.2 。

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