物理化学偏摩尔量ppt课件

1、 物理化学()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W0？（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) Characteristics of multi-component a

2、nd 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 5

3、0.68 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。 *,miiVnV(3) More than 3 independent variables are needed to define the state of a system. ),( 21nnpTfV 2. Partial molar quantitiesTaking volume

4、 as an example. For a system at thermal and mechanical equilibrium, we have ),( 21nnpTfV d)(d)( d)(d)(d 2,21,1,122121nnVnnVppVTTVVnpTnpTnnTnnpDefine:, c,BB)( npTnVVas partial molar volume of substance B Partial molar internal energyPartial molar enthalpyPartial molar entropy )( ,BBcnpTnUU )( ,BBcnpT

5、nHH )( ,BBcnpTnSSPartial molar volumes of H2O and CH3CH2OH at 25oCDiscussion: Partial molar quantities are intensive properties of a system. （强度性质） ),( 21xxpTfV 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的条件下

6、，在无限大的系统中加入1 mol B所引起系统体积的变化量。 Conditions: Constant T and p. For a mono-component system, )B( *mBVV 3. Two important equations of partial molar quantities (1) Additivity of partial molar properties (偏摩尔量的集合公式，或加和公式偏摩尔量的集合公式，或加和公式)在指定T，p 均不变的条件下 ),( 21nnfV V是nB的一次齐函数。根据齐函数的Euler定理 2211VnVnV即：BBB VnV(

7、2) Gibbs - Duhem equation dd)(d)(d BBB,2121nVppVTTVVnnTnnpAt constant T and p, dd BBBnVVFromBBBBBBdddVnnVVBy comparison, we have 0d BBBVnBBB 0d VxBBB VnVFor binary systems, (A+B),VA是nA的零次齐函数，根据齐函数的Euler定理 0 B,BABBknpTnVn 0 B,ABBAknpTnVn 0 BB,ABB,AAAnpTnpTnVnnVn0)()(,ABB,AAApTpTxVxxVxOr,Problem：集合公式和

8、：集合公式和Gibbs - Duhem 方程的方程的适用条件相同吗？适用条件相同吗？0)()(,ABB,AAApTpTxVxxVx0)()(,BBB,BAApTpTxVxxVxSimilarly,0)()(,BBB,AAApTpTxVxxVxWe 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 )( 1,2npTnfV )( 1221,221nVnVVnVVnpT(3) 截距法截距法定义: )( BBAxfnnVVm可以证明: )( )( ,BmAmB,BmBm

9、ApTpTxVxVVxVxVVVAVBVmxB0 1 3.2 Chemical potential and fundamental equations of thermodynamics for open system1. Chemical potentialDefine: )( ,BBcnpTnGas chemical potential of component B dd)(d)(d BBB,cBcBnppGTTGGnnTnnpFor closed system , dnB= 0 )G( )( CBCB,VpSTGnnTnnp dddd BBBnpVTSGSet : ),( ),( ),(

10、 212121nnVTfAnnpSfHnnVSfUDefine: ,)( )( )( cccnVTBABnpSBHBnVSBUBnAnHnUBB,BBB,BBB,BBB,Bdddd dddd dddd dddd npVTSGnVpTSAnpVSTHnVpSTUGAHUFundamental 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, ,B,B,B,BGAHUBBBBBBBBBBBBdddd dddd dddd dddd npVTSGnVpTSAnpVSTHnVpSTUDiscussion: B是强度性