《基础化学》英文教学课件：chapter-6.ppt

1、冻笔新诗懒写，寒炉美酒时温。冻笔新诗懒写，寒炉美酒时温。醉看墨花月白，恍疑雪满前村。醉看墨花月白，恍疑雪满前村。唐唐李白李白立冬立冬Chapter 6 1.Thermodynamic system and state function2.Energy conservation and heat of chemical reaction3.Entropy and Gibbs free energy4.The extent and equilibrium constant of chemical reactions 1.Thermodynamic System and State Function

2、Thermodynamics():is the study of the relationship between heat and other forms of energy(including electric energy and chemical energy,etc.)involved in a chemical or physical process.It is based on the first and the second thermodynamic law(empirical law).Chemical thermodynamics():Heat effect of che

3、mical reactions,direction and extent of chemical reactions.It does not consider if a chemical reaction really occurs or not.It does not deal with how a chemical reaction occur and the reaction rate.I.System and surroundings to be investigated.The substance or mixture of substances under study in whi

4、ch a change occurs is called the thermodynamic system.directly related to system.Everything in the vicinity of the thermodynamic system.1.Thermodynamic System and State Function can exchange matter as well as energy with its surroundings.can exchange energy but not matter with its surroundings.can e

5、xchange neither energy nor matter with its surroundings.1.Thermodynamic System and State FunctionII.Process()Isothermal():The temperature of the system remains constant,T=Tsurr=constant.Isobaric():The pressure of the system remains constant,p=psurr=constant.Isochoric():The volume of the system remai

6、ns constant,V=constant.Adiabatic():No heat exchange with the surroundings,Q=0.Cyclic():Final state=initial state,U=0.1.Thermodynamic System and State Function“Adiabatic”comes from the Greek words for“not passing through.”III.Properties of a systemMacroscopic properties of a system:Pressure,volume,te

7、mperature,mass,composition,.Extensive properties():proportional to the quantity(moles).Example:mass,volume.1.Thermodynamic System and State FunctionIntensive properties():not dependent on the quantity(moles).Example:pressure,temperature,composition.IV.State and state functionThe state()of a system i

8、s defined by all properties of the system.1.Thermodynamic System and State FunctionState State function(T,p,V,n)(U,H,S,G)A state function()is a property of a system.A state function depends only on its present state and is independent of any previous history of the system.State function:extensive an

9、d intensive properties.1.Thermodynamic System and State Function(1)The increment of a state function is only dependent on the of the system,but not the process.373 K1 atm298 K10 atmIsobaricIsobaricIsothermalIsothermal298 K1 atm373 K10 atm1.Thermodynamic System and State Function(2)It is not necessar

10、y to list out all properties to describe a state of a system.For example,the state equation of ideal gas:pV=nRT.p,V,T n1.Thermodynamic System and State Function1.Thermodynamic System and State FunctionV.Internal energy()Energy:can be briefly defined as the potential or capacity to move matter.the en

11、ergy associated with an object by virtue of its motion.1.EnergyEnergy can exist in different forms,including heat,light,electrical,and chemical energy,and these different forms can be interconverted.2km21E1.Thermodynamic System and State Function22km/s)(20kg6021m21E224smkg101.20The SI unit of energy

12、,kgm2s-2,is given the name ().The ()is a non-SI unit of energy commonly used,originally defined as the amount of energy required to raise the temperature of one gram of water by one degree Celsius.J4.184cal1(exact definition)9 Calorie/1 g4 Calorie/1 g1Calorie(大卡大卡)=1 kilocalorie (千卡千卡)=1000 calorie(

13、卡卡)=4.184 kJ1.Thermodynamic System and State Function the energy an object has by virtue of its position in a field of force.mghEp1.Thermodynamic System and State FunctionInternal energy(内能内能,U):The sum of the kinetic and potential energies of the particles making up a system is referred to as the i

14、nternal energy.2.Internal energy(U)The water as a whole has Ek and Ep.However,H2O molecules are made up of smaller particles,electrons and nuclei.Each of these particles also has kinetic and potential energy.U:extensive property;absolute value of U?U:state function,U=(U final-U initial )1.Thermodyna

15、mic System and State FunctionUEEEpktotThe total energy of a quantity of a substance equals the sum of its kinetic and potential energies as a whole plus its internal energy.Normally when you study a substance in the lab,the substance is at rest in a vessel.Its Ek as a whole is zero.Moreover,its Ep a

16、s a whole is constant and can be taken to be zero.In this case,VI.Heat(Q)and work(W)Two forms of energy exchange between a system and its surroundings.1.Thermodynamic System and State FunctionHeat flows from a region of higher temperature to one of lower temperature;once the temperature become equal

17、(thermal equilibrium),heat flow stops.You would not say that the system has heat,because heat is only an energy flow.is defined as the energy that flows into or out of a system because of a difference in temperature between the system and its surroundings.is the energy exchange that results when a f

18、orce moves an object through a distance;work equals W=F d.1.Thermodynamic System and State FunctionHeat is absorbed by the system:(endothermic,):Q 0;Heat is released by the system:(exothermic,):Q 0;Work done by the system:W W2 W1 1.Thermodynamic System and State FunctionJ560Heat and work are not sta

19、te functions,they are dependent on the specific process.Isothermal expansion of ideal gasp1,V1p2,V2pVp1,V1p2,V2pVp1,V1p2,V2pV(1)(2)(3)Process(3)is a reversible()process.W3=Wmax 1.Thermodynamic System and State Function 2.Conservation of Energy&Heat of ReactionI.The first law of thermodynamics()The f

20、irst law of thermodynamics states that the internal energy of an system is constant.For,the mathematical expression of the first law of thermodynamics:U=Q+WEnergy can never be created or destroyed in ordinary chemical reactions and physical changes,it can only transform from one form to another.2.Co

21、nservation of Energy&Heat of Reaction This system gains internal energy from the heat absorbed(165 J)and loses internal energy via the work done(92 J).Thus the net change of internal energy is:J73J)92(J)165(WQUFritz Haber(1868-1934)Nobel Prize Chemistry(1918)Haber Process（哈伯循环（哈伯循环）(g)NH2(g)H3(g)N32

22、22.Conservation of Energy&Heat of Reaction 2.Conservation of Energy&Heat of ReactionII.Heat of reaction()Two crystalline substances,Ba(OH)28H2O and NH4NO3,are mixed thoroughly in a flask.Then the flask,which feels quite cold to the touch,is set in a puddle of water on a board.In a couple of minutes,

23、the flask and board are frozen solidly together.The board can then be inverted with the flask frozen to it.2.Conservation of Energy&Heat of Reaction(at a given temperature)is the value of Q required to return a system to the given temperature at the completion of the reaction.23233422)Ba(NOOH10NH2NO

24、NH2OH8Ba(OH)OH2COO2CH2224kJ170.4Q(endothermic)1 mol Ba(OH)2,kJ890Q(exothermic)1 mol CH4,2.Conservation of Energy&Heat of ReactionMeasurement of heat of reaction(here the heat of combustion of graphite).Bomb calorimeter():a device used to measure the heat absorbed or released during a physical or che

25、mical change.(g)CO(g)OC(gra)22Biocalorimetry(生物量热学生物量热学)微量量热技术微量量热技术 10 20 30 40 t/h（1）ADSE用肉胨培养的细菌特征热谱图用肉胨培养的细菌特征热谱图（2）ADSF用肉胨培养细菌用肉胨培养细菌26h后加抗生素的细菌特征热谱图后加抗生素的细菌特征热谱图2.Conservation of Energy&Heat of ReactionIII.Isochoric reaction heat()U=QV+W=QV+p V=QVConsider a chemical reaction under an isochoric

26、 conditions(Q=QV,V=0):U=QVThe heat of reaction at constant volume(isochoric reaction heat)equals the change in internal energy for the reaction.2.Conservation of Energy&Heat of ReactionIV.Enthalpy()and isobaric reaction heat()U=Ufinal Uinitial=Qp+WConsider a chemical reaction under an isobaric condi

27、tions(Q=Qp):For isobaric process:pinitial=pfinal=pout,then:(Ufinal+pfinalVfinal)(Uinitial+pinitialVinitial)=QpH U+pV(definition)2.Conservation of Energy&Heat of ReactionW=-pout V=-pout(Vfinal Vinitial)H=QpHfinal Hinitial=Qp2.Conservation of Energy&Heat of ReactionH:,state function,extensive properti

28、es.The heat of reaction at constant pressure(isobaric reaction heat)equals the change in enthalpy for the reaction.H U+pV U=QV U=Q+WQV=Qp+WQV=Qp-P V(s.l,nn=0)QV=QpQV=Qp-P V(g)Q p=QV+nRT n=n(products)-n(reactants)2.Conservation of Energy&Heat of ReactionExample:298K，1atm，2 mol H2 and 1 mol O2 were mi

29、xed,and 2 mol H2O(l)was produced after a certain time.Calculate the extent of reaction of isochoric reaction heat and isobaric reaction heat,1 mol H2O(l)was produced.2H2(g)+O2(g)=2H2O(l)Q=-571.6 kJ mol-1Solution:Qp=-285.8 kJ mol-11 mol H2O(l)was produced n=n(products)-n(reactants)=-3 nRT=-7433 J=-7.

30、4 kJQp=QV+nRT2.Conservation of Energy&Heat of ReactionQp=QV+nRTQV=Qp-nRT=-282.1 kJ mol-1QV Qp1 mol H2O(l):nRT=-3.7 kJ mol-1Qp=-285.8 kJ mol-1 H=Qp U=QV H U2.Conservation of Energy&Heat of ReactionThe change in enthalpy for a reaction at a given temperature and pressure(H,also called the enthalpy of

31、reaction,)is obtained by subtracting the enthalpy of the reactants(initial state)from the enthalpy of the products(final state).(g)HNaOH(aq)2O(l)H2Na(s)222H(initial)H(final)H)H(HNaOH)H(22O)HH(2Na)H(22s)H(reactant)H(products V.Extent of reaction()BBB0For a reaction:B:reactants or products;B:stoichiom

32、etric coefficient of B;B(product)0;B(reactant)0.BBnExtent of reaction(ksai):2.Conservation of Energy&Heat of ReactionhHgGfFeEfFeEHhgG0Example 6-1:10.0 mol H2 and 5.0 mol N2 were mixed,and 2.0 mol NH3 was produced after a certain time.Calculate the extent of reaction of(1)and(2).(1)(2)(g)NH2(g)H3(g)N

33、322(g)NH(g)H(g)N3223221Solution:According to reaction(1):mol1.01mol1.0)(N)n(N)(N2222.Conservation of Energy&Heat of ReactionTo produce 2.0 mol of NH3,1 mol of N2 and 3 mol of H2 were consumed,respectively.mol1.0)n(N2mol3.0)n(H2mol2.0)n(NH3mol1.03mol3.0)(H)n(H)(H222According to reaction(2):mol2.0mol1

34、.0)(N)n(N)(N21222mol2.0)(NH)(H322.Conservation of Energy&Heat of Reactionmol1.02mol2.0)(NH)n(NH)(NH333Extent of reaction remains the same no matter which reactants or which products are used to calculate it.Extent of reaction is a function of stoichiometric coefficient of reactants and products.VI.T

35、hermochemical equations()2.Conservation of Energy&Heat of Reaction H:isobaric reaction heat(enthalpy of reaction);Definition:the chemical equation for a reaction(including phase labels)in which the enthalpy of reaction(H)is written directly after the equation.1mr222molkJ285.83HO(l)H(g)O21(g)H“r”:rea

36、ction;mol1l)O,n(Hn2BB“m”:=1 mol;:standard state.2.Conservation of Energy&Heat of ReactionThe temperature is 298.15 K(25 C)if otherwise stated.Pure Gas&Pure Liquid:p=100 kPa(1 bar).Standard state():The standard thermodynamic conditions chosen for substances when listing or comparing thermodynamic dat

37、a:standard pressure p (100 kPa,1 bar)and the(any)specified temperature(usually 25 C).Solute(in solution):p=100 kPa,c=1 mol L-1.2.Conservation of Energy&Heat of ReactionThe standard state used to be defined for 1 atm rather than for 1 bar;however,the latter is now the accepted standard.The small chan

38、ge in standard pressure makes a negligible difference to most numerical values,so it is normally safe to use tables of data compiled for 1 atm.1mr222molkJ285.83HO(l)H(g)O21(g)HThis equation says that,at 25 C,1 mol of hydrogen gas(partial pressure of 100 kPa)reacts with one-half mol of oxygen gas(par

39、tial pressure of 1 bar)to produce 1 mol of liquid water(partial pressure of 1 bar),and 285.83 kJ of heat is released.1mr222molkJ241.8HO(g)H(g)O21(g)H2.Conservation of Energy&Heat of Reaction183.285molkJHmr H2(g)+1/2O2(g)=H2O(l)Notes:1.When a thermochemical equation is by any factor,the value of H fo

40、r the new equation is obtained by multiplying the value of H in the original equation by the same factor.2.When a chemical equation is,the value of H is reversed in sign.183.285molkJHmr H2O(l)=1/2O2(g)+H2(g)166.571molkJHmr 2H2(g)+O2(g)=2H2O(l)183.285molkJHmr H2(g)+1/2O2(g)=H2O(l)2.Conservation of En

41、ergy&Heat of ReactionVII.Fuels()A is any substance that is burned or similarly reacted to provide heat and other forms of energy.The human body requires about as much as energy in a day as does a 100-watt lightbulb.1.Foods as fuels.O(l)H6(g)CO6(g)O6(s)OHC22261261gkJ15.6O(l)H43(g)CO45(g)O(s)OHC222212

42、7686451gkJ38.5Carbohydrate:Fat:2.Conservation of Energy&Heat of ReactionPetroleum supplies will be 80%depleted at about the year 2030.Natural-gas supplies may be depleted even sooner.Coal supplies are sufficient to last several centuries.This abundance has spurred much research into developing comme

43、rcial methods for converting coal to more easily handled liquid and gaseous fuels.2.Fossil fuels.1gkJ30.6O(g)H9(g)CO8(g)O(l)HC2222251881gkJ44.4Solid Coal():Liquid petroleum():Natural gas():O(g)H2(g)CO(g)O2(g)CH22241gkJ50.12.Conservation of Energy&Heat of Reaction3.Rocket fuels.O(g)H13(g)CO12(g)O(l)H

44、C22223726121gkJ44.1The first stage of the Saturn V launch vehicle(that sent a three-man Apollo crew to the moon)used:An unbelievable 550 tons of were burned in 2.5 minutes(1.62 1011 watts).The second and third stage of liftoff used liquid hydrogen(b.p.253 C)/oxygen(b.p.183 C)system:O(g)H(g)O(g)H2221

45、21gkJ1202.Conservation of Energy&Heat of ReactionThe landing module for the Apollo mission used a fuel of hydrazine and an oxidizer of dinitrogen tetroxide:O(g)H4(g)N3(l)ON(l)HN22242421gkJ16.3Solid fuels(containing aluminum metal powder and other materials with ammonium perchlorate as the oxidizer)w

46、ere used in the booster rockets of the Columbia space shuttle.A cloud of aluminum oxide forms as the rockets burn.VIII.Hesss lawHesss law states that for a chemical equation that can be written as the sum of two or more steps,the enthalpy change for the overall equation equals the sum of enthalpy ch

47、anges for the individual steps.2.Conservation of Energy&Heat of ReactionNo matter how you go from given reactants to products,the enthalpy change for the overall chemical change is the same.reactantsproducts2.Conservation of Energy&Heat of Reaction(g)CO(g)OC(gra)22CO(g)(g)O21C(gra)2(g)CO(g)O21CO(g)(

48、g)OC(gra)222.Calculating the isobaric reaction heat(enthalpy of reaction)1.From known thermochemical equations:Example 6-2:(1)C(gra)+O2(g)=CO2(g)11,5.393molkJHmr(2)CO(g)+O2(g)=CO2(g)12,0.283molkJHmrCalculate the enthalpy of the following reaction:(3)C(gra)+O2(g)=CO(g).2.Conservation of Energy&Heat o

49、f ReactionSolution:m,2rm,3rm,1rHHHm,2rm,1rm,3rHHH2.Conservation of Energy&Heat of ReactionC(gra)+O2(g)=CO2(g)CO(g)+O2(g)=CO2(g)11,5.393molkJHmr12,0.283molkJHmrC(gra)+O2(g)=CO(g)13,5.110molkJHmrThermochemical equations for the individual steps of a reaction sequence may be combined to give the thermo

50、chemical equations for the overall reaction.2.Conservation of Energy&Heat of ReactionC(gra)+O2(g)=CO2(g)CO(g)+O2(g)=CO2(g)C(gra)+O2(g)-CO(g)=0C(gra)+O2(g)=CO(g)CO(g)=C(gra)+O2(g)2.From standard molar enthalpies of formationmfHStandard molar enthalpy of formation()of a substance is the enthalpy for t