2.1.3ProcessandPathway(1)Theprocessofstatechangeisnamedaspathway,suchasisothermalprocess,isobaricprocess,isochoricprocess(2)In these regards,the process that a system experiencesfromtheinitialstatetothefinalstateisnamedasthepathstate.(3)Fromstate1tostate2,thepathwayisdifferent,butthechangevaluesofparametersinstatefunctioncanbethesame.(4)Whenthestateisfixed,thenumericalvaluesinthestatefunctioncanbeprovided.(5)Asfarastheinitialandfinalstatesaredetermined,thechangedvaluesofparametersinthestatefunctionpresentonlynumber.(6)Forisobaricprocesses,Pisequaltozero.Forisochoricprocesses,V is equal to zero,For isothermal process,T isequaltozero.298K，101.3kPa298K，506.5kPa375K，101.3kPa375K，506.5kPaIsothermalprocessPath(II)IsochoricprocessPath(I)(I)Isobaricprocess(II)actualprocessTheactualprocessandthedesignedprocessaredifferentIsothermalprocess2.1.4phase：Thephysicalandchemicalpropertiesinthefixedsystem are same,in which the homogeneous part isdefinedasaphase.Thereisaclearinterfacebetweenthephases.SinglephasesystemAccordingtothephasenumbersinthesystem：Multiphasesystem(twophase,threephase)Water(l)SugarwaterSugarwatersugar homogeneoussystemmultiphasesystem 2.1.5stoichiometricequationandreactionprogress(1)Thestoichiometricequation:chemicalreactionequations.(2)Thecorrectchemicalformula(3)Whetherreactantorreactionproduct,itshouldindicateitsspecificstate:g,l,s,aq.(4)Theconservationofatomandcharge.Thestoichiometriccoefficients:thecoefficientsatthefrontoftheformulahavetobesignedplusorminus.Thecoefficientofreactantsisnegative,otherwise,otherspositive.aA(g)+bB(g)=gG(g)+dD(g)A=-aB=-bG=gD=dReactiveprogress():inordertoelucidatethatthe chemical reaction is going on,Donder,theBelgianchemist,proposedaconcept.Itsunitisexpressedinmole.aA+bB=gG+dDExample1:when3molesofnitrogenreactwithtenmolesofhydrogenthroughthereactiontowerandthengothroughmanycycles,finally,2molesofammoniaisgenerated.valuecouldbecalculatedusingfollowingtworeactionequations:(a)N2+3H2=2NH3(b)1/2N2+3/2H2=NH3Thephysicalmeaningof=1mole:thereactionachievesaunitreactionaccordingtothecoefficientproportionofthestoichiometriccoefficientforreactionformula:(1)Thevaluemustbecorrespondingtothestoichiometricreactionformula.(2)Forthesamechemicalreactionformula,thecalculatedvalueexpressedbyreactiveorproductivesubstanceisthesame.nB/mol 3.0 10.0 0 0 nB/mol 2.0 7.0 2.0nB/mol 1.5 5.5 3.0 t=t0:t=t1:t=t2:2.0 7.0 2.0 (mol)3.0 10.0 0 (mol)t=0t=t1(1)Thevaluemustbecorrespondingtothestoichiometricreactionformula.(2)Forthesamechemicalreactionformula,thecalculatedvalueexpressedbyreactiveorproductivesubstanceisthesame.