10 Reaction Equations要点.docx
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10 Reaction Equations要点.docx
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10ReactionEquations要点
10.REACTIONEQUATIONS
ClickingtheReactionEquationsbuttoninthemainmenushowstheReactionEquationsWindow,seeFig.1.Withthiscalculationoptionyoucancalculatetheheatcapacity,enthalpy,entropyandGibbsenergyvaluesofasinglespeciesaswellasofspecifiedreactionsbetweenpuresubstances.
Seethereferencestatedefinitions,validnotationsandabbreviationsforthedescriptionofthechemicalformulaeinChapter28.Databases,chapter2.
10.1OneChemicalSubstance
Fig.1.ReactionEquationsWindowofHSCChemistry.
Fig.2.ThermodynamicdataofA12O3(alumina)displayedbytheReactionEquationoptionofHSCChemistry.
ByenteringasinglechemicalformulaintotheFormulaboxyouwillgetsimilartablesofthermochemicaldataaspresentedinmanythermochemicaldatabooks.HSCwill,however,providetheresultsfasterandexactlyatthosetemperatureswhichyoureallywant.Pleasefollowthesesteps:
1.Writeachemicalformulaintothebox,Fig.1.
Forexample:
Fe,Na2SO4,Al2O3,SO4(-a),H(+a)orSO2(g).
SeethevalidnotationandsyntaxofchemicalformulaeinChapter21.2.
2.Selectthelowerlimit,upperlimitandtemperaturestep.
3.SelecttheTemperatureandEnergyUnits,byclickingthecorrespondingbuttons.
4.SelecttheFormatoftheresults.
Normal(Absolutescale):
H(species),S(species)andC(species)
ThisformatisusedforexampleinthefamousI.Barin,O.Knacke,andO.Kubaschewskidatacompilation1.
Delta(Formationfunctions):
∆H=H(species)-∑H(elements)
∆S=S(species)-∑S(elements)
∆G=G(species)-∑G(elements)
∆G=G(ions)-∑G(elements)+z/2*G(H2(g))-z*G(H(+a))
z=charge.
ThisformatisusedforexampleintheNBSTablesNBS82.
5.TheCollecttoSheetoptionwillcollectseveraltablesonthesamespreadsheet.
6.SelecttheShowTransitionsoptionifyoualsowanttoseethedataatthephasetransformationtemperatures,suchascrystalstructurechangesandmelting.
7.SelecttheCriss-CobbleoptionifyouwantaCriss-Cobbleextrapolationfortheheatcapacityofaqueousspecies,seeChapter21.4.
8.PressCalculate(orEnter)togettheresultsonthescreen.
9.PressPrinttoprinttheresults,seeFig.2.NotethatyoucancollectseveralsetsofresultsinthesamesheetifyouhaveselectedtheCollecttoSheetoptioninFig.1.YoucanclearthewholesheetbypressingClear.
10.PressCopyAlltogetalltheresultsintotheClipboard,thenyoucaneasilypastetheresultstootherWindowsapplications,forexample,toMS-Excel,seeFig.2.UsingCopyitispossibletocopyandpastecontentsofindividualcellstootherapplications.
11.IfyouwanttosavetheformulaandresultsinanASCII-filepressSave,seeFig.2.YoucanreadthesefilesbacktotheReactionmoduleusingFileOpen,seeFig.1.NotethatSavesavesalltheselectionsinFig.1,soyoucanreturntheseusingFileOpen.TheFileOpenHSC2FilebuttonreadsonlyoldHSC2.0fileswhichreturnonlyformula,butnottheselectionsnortemperaturerange.
Note:
1.Youcaneasilycheckthebasicdatafromthedatabase,whichhasbeenusedinthereactionmodulecalculations.InFig.1selecttheformulaintheReactionEquationboxandpressPeepDatabase.ThesameprocedurecanbefoundinFig.2bypressingtherightmousebuttonorselectingEditfromthemenu.
2.ThetableinFig.2hassomeformattingandCopy-PastefunctionsasdoothertablesinHSCChemistry.Thesefeatureshelptocreateagoodprintedcopyoftheresultsforvariouspurposes.
3.HSCsearchesforthespeciesdatafirstfromtheOwndatabase(OwnDB5.HSC).Ifitdoesnotfindaspeciesthere,itwillsearchfromtheMaindatabase(MainDB5.HSC).ThereforeHSCalwaysusesdataintheOwndatabaseifthesamespeciesexistsinbothOwnandMaindatabases.
4.IfyouhaveselectedDelta-formatfortheresults,HSCwillalsosearchfordataforthenecessaryelementsandcalculatetheformationfunctionsofenthalpy,entropyandGibbsenergy.Usuallytheoriginalexperimentaldataisinthisformat:
however,sometimesthecomparisonofdatainthisformatmaybemoredifficultbecausethedatasourcesoftenusedifferentdataforelements.
5.HSCwillmakeaCriss-Cobbleextrapolationfortheheatcapacityofaqueousspeciesatelevatedtemperatures(>25C°)iftheCriss-Cobbleoptionisselected.TheextrapolationisnotdoneifAandBoftheheatcapacitycoefficientsA,B,CandDexistintheHSCChemistrydatabases.Theextrapolationerrorincreasesrapidlyathighertemperatures.MoreinformationonextrapolationisgiveninChapter28.4.
6.Foraqueousspeciesitisrecommendedtoset:
Lowertemperature=25°C
Uppertemperature=300°C
Step=25°C
10.2OneChemicalSubstanceResults
AfterpressingtheCalculatebuttoninthepreviousscreen,Fig.1,youwillarriveintheresultswindow,Fig.2.Fromthisresultsscreenyoucansaveandprinttheresults:
1.PressSaveifyouwishtorecalculatetheresultslater.TheSavebuttonwillalsosavethesettingsusedinFig.1.YoucanreadthesefilesbacktoHSCusingtheFileOpenbutton,seeFig.1.
2.PressPrintifyouwantapapercopy.IfyouhaveselectedtheCollecttoSheetoptioninFig.1,thenallresultswillbecollectedonthesamesheetandcanbeprintedtogether.Clearwillcleartheresultssheet.
3.PressCopytogettheresultsofselectedcellsintotheClipboard,thenyoucaneasilypastetheresults,forexample,toMS-Excel,seeFig.2.
4.PressCopyAlltogetalltheresultsofthesheetintotheClipboard,thenyoucaneasilypastetheresults,forexample,toMS-Excel,seeFig.2.
5.PressOKtoreturntothepreviousWindow.
10.3ReactionEquations
Fig.3.InputdataforReactionEquationcalculations.
Fig.4.ResultsofReactionEquationcalculations.
YoucanwritealmostanykindofreactionequationintotheReactionEquationboxofHSC,Fig.3.Herearesomeexamplesofvalidequationsyntax:
2Cu+S=Cu2S
H2O=H(+a)+OH(-a)
H2(g)=2H(+a)+2e-
H2O=1/2O2(g)+2H(+a)+2e-
Ag=Ag(+a)+e-
3NO2(-a)+2H(+a)=2NO(g)+H2O+NO3(-a)
2Al(+3a)+3S(-2a)+6H2O=2Al(OH)3+3H2S(g)
Writethereactionequationintothebox,seeFig.3.Ifyouhavenotgiventhestoichiometriccoefficientsforthespecies,youcanpressBalanceEquationforsolvingunknowncoefficients.Thebalancebuttonsolvesthecoefficientsonthebasisofelementbalanceequations.Thereforeitcannotsolveunknowncoefficientsiftheirnumberislargerthanthenumberofelementsinthecorrespondingreaction.
Ontherightsideofthebuttonyoumaygiveamultiplier,whichwillbeusedtomultiplyallthecoefficientsinthereactionequation.Thedefaultvalueis1,whichmeansthatthesmalleststoichiometriccoefficientinthereactionequationis1.
YoucancontinueinthesamewayasintheOneChemicalFormulaoptionChapter10.1.NotethattheDeltaFormatandShowTransitionsoptionshavenoeffectontheresults,becausetheenthalpyandGibbsenergyofareactionareintheDeltaformatbydefinition.
HSCcalculatesthestoichiometryofthereactiongivenbytheuser,andpointsouterrorsiftheelementbalanceisincorrect.
TheexampleinFig.3referstotheMond-processforrefiningimpurenickel.IntheprocessrawimpurenickelisfirsttreatedwithCOgasat60°Ctoevaporatethenickelasacarbonylgas.Inthesecondstage,thetemperatureofthegasisincreasedto200°CtodecomposethenickelcarbonylgasintopuremetallicnickelandCO.Thisprocessworksbecausetheequilibriumofthisreactionisontherightside(EquilibriumconstantK>1)atlowertemperaturesandontheleftside(K<1)athighertemperatures.Thereactionisexothermic(DHisnegative)atalltemperatures.
Vaporpressurespcanbecalculatedbywritingthereactionequationforthevaporizationreactionconcerned.Forexample,forpuremagnesiumtheequilibriumisMg=Mg(g),Fig.5.Theactivityaofpuremagnesiumis1andthusthevaporpressureinbarisequaltotheequilibriumconstantaccordingtoEq.(10)inChapter8.IntroductionandEq.
(1).SeealsoFig.6.
K=pMg/aMg=pMg[1]
Ifasubstancevaporizesintoseveralpolymers,allofthemmustbetakenintoaccount.Thetotalvaporpressureisthenthesumofalltheindividualpartialpressures,ifthegasphasebehavesideally.
Youcanalsocalculatemorecomplicatedreactions.FirstwritethereactionasshowninFig.7,thenpressBalanceforthecoefficients,seeFig.8andfinallypressCalculatefortheresults,seeFig.9.NotethatforaqueousionicreactionsHSCalsocalculatestheelectrodepotentialversusStandardHydrogenElectrodeifelectron(e-)isusedintheformula.
Youcancalculatemassbalancesinmoles,gramsandlitersforanyreaction.ThespeciesdoesnotneedtoexistintheHSCdatabases.
Fig.5.InputdataforReactionEquationcalculations.
Fig.6.TheequilibriumconstantKisequaltothevaporpressureinatmaccordingtoEquation
(1)iftheactivityofmagnesiumis1.Theboilingpointofmagnesiumisabout1100°Cbeyondwhichitsvaporpressureexceeds1atm.
Fig.7.WritethereactionequationwithoutstoichiometriccoefficientsandpressBalanceEquation.
Fig.8.PressCalculatetodisplaytheresults.
Fig.9.Resultsforanaqueousionicreaction.
ThedatausedtocalculatetheresultscanbedisplayedbyselectingonesubstanceintheReactionEquationbox,seeFig.3andpressingPeepDatabase.ThesameprocedurecanbefoundintheResultswindow,seeFig.4,bypressingtherightmousebutton.ThedatabasecontentisshowninFig.10.InsertisavailableforinsertingaselectedformulaintotheReactionEquationbox.Removewillremoveaselectedformulafromthissamebox.Notethatthese
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