Contents of Today S.J.T.U. Phase Transformation and Applications Review previous On Gibbs free energy Electrochemical Nomenclature Calculation of Cell voltage Direction of Reaction etc. SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I Contents of Today Review previous On Gibbs free energy Electrochemical Nomenclature Calculation of Cell Voltage Direction of Reaction etc
5.1 THERMODYNAMIC ACTIVITY (2) S.J.T.U. Phase Transformation and Applications No Units 三 Reference state:temperature,pressure and physical form Standard state:pressure and physical form Gas:pure gas at one atmosphere Condensed mater:pure liquid or solid under one atmosphere CdG,-G,-G=RTn人-RTna dG,-G,-G;=RTIn P=RTIna, Ideal gas The fugacity of a condensed phase is equal to the fugacity of the vapor in equilibrium with it. The value of thermodynamic activity changes not only with pressure but also with composition SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I 5.1 THERMODYNAMIC ACTIVITY (2) D i i i f f α ≡ i i i i i G G i RT ff =−= RTGGdG ln = lnα ∫ D D D i i i i i G G i RT PP =−= RTGGdG ln = lnα ∫ D D D Ideal gas No Units Reference state: temperature, pressure and physical form Standard state: pressure and physical form Gas: pure gas at one atmosphere Condensed mater: pure liquid or solid under one atmosphere The fugacity of a condensed phase is equal to the fugacity of the vapor in equilibrium with it. The value of thermodynamic activity changes not only with pressure but also with composition
5.2 CHEMICAL EQUILIBRIUM S.J.T.U. Phase Transformation and Applications bB+cC=dD+eE Expression for a chemical reaction OWron=AG=dGD+eGE-bGB-cGc GB =GB+RTInag AG=d(Gi+RT Inap)+e(Gi RTInag)-b(GB+RT Inag)-c(Gc+RT Inac) △G=△G°+RTIn J G=0 △G°=dG)+eGE-bGB-cG& Equilibrium constant d。 e J b △G°=-RTInm）)=-RTIn K SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I 5.2 CHEMICAL EQUILIBRIUM + = + eEdDcCbB δ rev D E B −−+=Δ= GcGbGeGdGW C )ln()ln()ln()ln( D +=Δ RTGdG α D E ++ RTGe α E B +− RTGb α B C +− RTGc α C D D D D α +Δ=Δ ln JRTGG D D D D D D D E B C −−+=Δ cGbGeGdGG c C b B e E d D J αα αα α = B BB += RTGG lnα D α KRT α JRTG mequilibriu −=Δ ln ( ) −= ln D Equilibrium constant Expression for a chemical reaction ΔG 0 =
5.6 ELLINGHAM DIAGRAMS (4) S.J.T.U. Phase Transformation and Applications 101010410 1. 直线位置越低，元素与氧 化合的能力越大，相应的 7402w0 氧化物越稳定； 7 2. 位置在下的金属或元素可 以把较上面的金属从氧化 物中还原出来； 00-00 3. 炼铁过程，铁以下进入炉 渣，铁以上进入铁液，决 定何时加入配料。 期0-子，03 局限 202…2g0 平衡的热力学讨论 1000 10-e 凝聚相都是纯物质 Figure 5.7 Ellingham diagram for some oxides. SJ I U Inermodynamics ot Materials Spring 2UU6 ©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I 5.6 ELLINGHAM DIAGRAMS (4) 1. 直线位置越低，元素与氧 化合的能力越大，相应的 氧化物越稳定； 2. 位置在下的金属或元素可 以把较上面的金属从氧化 物中 还原出来； 3. 炼铁过程，铁以下进入炉 渣，铁以上进入铁液，决 定何时加入配料。 局限 平衡的热力学讨论 凝聚相都是纯物质
5.7 VARIATION OF EQUILIBRIUM CONSTANT WITH TEMPERATURE S.J.T.U. Phase Transformation and Applications d(△G)=-△SdT △G°=△H°-T△S dAG)=△Cdr- H°dr T T Multiplying by 1/T,we obtain: T aag)=a-RInK.）)=AHrd宁） SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I 5.7 VARIATION OF EQUILIBRIUM CONSTANT WITH TEMPERATURE Multiplying by 1/T , we obtain: dTSGd D D )( Δ−=Δ D D D Δ−Δ=Δ STHG dT T H dT T G Gd D D D Δ − Δ )( =Δ dT T H dT T G T Gd 2 2 )( D D D Δ −= Δ − Δ ) 1()ln()( T dHKRd TG d D D Δ=−= Δ α ) 1 )(ln (T d RH Kd D Δ α −= G 1 d( ) H d( ) T T Δ = Δ D D
5.8 GASES DISSOLVED IN METALS (SIEVERT'S LAW) S.J.T.U. Phase Transformation and Applications H2(g)=2H (in copper solution) 0H,(g) an [H] 1.0 IHp 1 cm3(STP)/100 gCu [H](concentration of H)-> Figure 5.10 Plot of activity of dissolved hydrogen versus [H]=K&2P2 concentration. SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I 5.8 GASES DISSOLVED IN METALS (SIEVERT’S LAW) 2)( HgH (in copper solution) 2 = )( 2 2 gH H K α α α = α H = [ ] H [ ] 2 2 PH H Kα = [ ] 2/12/1 H2 = α PKH
5.9 CHEMICAL EQUILIBRIUM AND ADLABATIC S.J.T.U. FLAME TEMPERATURES 1) Phase Transformation and Applications Not completion First law Chemical equilibrium Chemical equilibrium Egs 5.36a and 5.36b First law (Chemical equilibrium) 0.8 Eq.5.37(AFT) 0. 人 0.4 0.2 0 2,000 4,000 6,000r·8,000 10,00012,00014.000 Tempperature (K)-> Figure 5.11 The extent of the reaction 2H-H,as a function of temperature for the AFT and chemical equilibrium calculations (Egs.5.37 and 5.36a, respectively). SJTU Thermodynamics of Materials Spring2o06©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I 5.9 CHEMICAL EQUILIBRIUM AND ADLABATIC FLAME TEMPERATURES (1) Not completion First law Chemical equilibrium First law Chemical equilibrium
On Gibbs free energy S.J.T.U. Phase Transformation and Applications -d(G),p≥-w' 只要有状态变化就有dG,但此时一dG不一定是系统的最大有 效功。 如果在定温定压下的可逆过程中，系统对环境作有效功，则 此时系统的Gibbs自由能必然减少，就是自发过程； 如果在定温定压下的可逆过程中，需要环境对系统做功，则 就是不自发过程。 因此，在定温定压条件下，只要根据dG的正负号就可判断过 程是否自发进行。并不需要知道实际过程的热温商，很多过 程，特别是化学反应，通常在定温定压下进行，因此，G这 个函数显得特别重要！ SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I On Gibbs free energy ( ) ' , WGd pT ≥− −δ 只要有状态变化就有dG，但此时－dG不一定是系统的最大有 效功。 如果在定温定压下的可逆过程中，系统对环境作有效功，则 此时系统的Gibbs自由能必然减少，就是自发过程； 如果在定温定压下的可逆过程中，需要环境对系统做功，则 就是不自发过程。 因此，在定温定压条件下，只要根据dG的正负号就可判断过 程是否自发进行。并不需要知道实际过程的热温商，很多过 程，特别是化学反应，通常在定温定压下进行，因此，G这 个函数显得特别重要！
Index of nomenclature S.J.T.U. Phase Transformation and Applications Electrochemicali电化学 Electrochemical cell电化学电池 Electrode电极 Electrolyte电解液 Oxidation氧化/anode阳极 Reduction还原/cathode阴极 Electrical work电功 Electromotive force(emf电动势 ·Faraday constant法拉第常数96480C.mo1 ·Half-cell reaction半电池反应 SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I Index of nomenclature • Electrochemical电化学 • Electrochemical cell 电化学电池 • Electrode 电极 • Electrolyte 电解液 • Oxidation 氧化 / anode 阳极 • Reduction 还原 / cathode 阴极 • Electrical work 电功 • Electromotive force (emf) 电动势 • Faraday constant 法拉第常数 96480 C.mol-1 • Half-cell reaction 半电池反应
Introduction(1) S.J.T.U. Phase Transformation and Applications Equilibrium:no reversible work could be done.The reactants and products were assumed to be in contact with one another. WrRer =VG=0 Doing work on the system. Work derived directly from chemical reactions. Conversion efficiency:1/3 Second law limitation inefficiency by friction SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 10 electrochemistry I
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 10 electrochemistry I Introduction(1) Equilibrium: no reversible work could be done. The reactants and products were assumed to be in contact with one another. = ∇GW = 0 rev Doing work on the system. Work derived directly from chemical reactions. Conversion efficiency: 1/3 Second law limitation + inefficiency by friction