高中化学计算题High school chemistry problemWord下载.docx
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4X(gas)+3(gas)Y(gas)2q+nR(gas)afterreachingbalance,container,constanttemperatureofmixedgaspressureincrease5%thantheoriginal,Xconcentrationdecreasestoathird,isthevalueofninthereactionequation
A.3B.4C.5D.6
Solutionone:
grasp"
theconcentrationofXdecreasesby1/3"
thecoefficientratioofthecombinationofchemicalequationisequaltovolumeratio,canlistthebeginningstate,variableandfinalstateofeachsubstanceseparately:
4x3y2qnR
Theinitialstateis3L,2L,0,0
Variable-athird*3l=1l-3/4+2/4=3/4l*1*1ll=1/2l=n+n/4*1l/4l
Thefinalstateis3minus1isequalto2L2minus3/4isequalto5over4L0plus1/2isequalto1over2L0plusnover4isequaltonover4liters
Relationbyaboveknowable,balance(final)aftermixingthevolumeofagasof5/4(2++1/2+n/4)L(15+n)/4L,accordingtothequestion"
thantheoriginalmixedgaspressureincreasedby5%(15+n)/4to5=5*5%,n=6areobtained.
Method2:
choosedifferencemethod,accordingtothequestionof"
mixedgaspressurethantheoriginalincreasedby5%,"
accordingtothequestion"
thantheoriginalmixedgaspressureincreasedby5%,thevolumeofthemixedgasincreasesthe(2+3)*5%=0.25L,accordingtotheequation,4X+3ycanonlygenerate2q+nR,namelyevery4Xreactionvolume,totalvolumechangequantityforthe(2+n)-(4+3)=n-5,existing=1/3*3LLXreaction,namelythevolumechangeof1L*(n-5)/4=0.25L,soastocalculaten=6.
Method3:
seizethe"
mixedgaspressurethantheoriginal5%increase"
itisconcludedthatatthebeginningofthereactionbyX+Y,balancemustshifttotherightfirst,aftergeneratingQandR,thepressureincrease,showpositivereactioniscertainlyincreasethereactionvolume,thesumofthereactionequationcoefficientofXandYwillbelessthanthecoefficientofthesumofQandR,so4+3<
2+n,itisconcludedthatthen>
5,inthefouroptionsthataccordswitharequirementonlyDn=6,forthepersonstobetheanswer.
Subjecttestisaboutthecontentofthechemicalequilibrium.Asolutionistofollowthelawofchemicalequilibrium,asaccordingtothespecification,althoughcancertainlyworkoutthecorrectanswer,butdidnothold"
choice,don'
task,don'
tprocess,aslongastheresults,thecharacteristicsofcalculatedasatopictodo,theordinarystudentalsoshoulduseatleast5minutestocomplete,spendmoretime.Methodusingdifferencemethod,withthevolumeofnvariables(delta),toestablishtheequationfor豱RanXiaworkedoutthevalue,butstillfailedtomakefulluseofthe"
choice"
characteristicsofmultiplechoice,availabletoabout1minutes.Solutionthreeunderstandingontherelationshipbetweenthebalanceofmobileandvolumechange,nothalfaminutecanbeconcludedthattheonlycorrectanswer.
Thus,intheprocessofcalculationaccordingtothecharacteristicsofthesubjectchoosesdifferentproblemsolvingmethods,oftencouldhelpintheprocessofreducingoperationtimeandthechanceoferror,toachievefastandaccuratetheeffectofproblemsolving,andusemoreproblemsolvingmethodusuallyhasthefollowingkinds:
Quotientmethod:
thismethodisusedtosolvethemolecularweightoforganiccompounds(especiallyhydrocarbons).
BecauseofalkanesgeneralformulaCnH2n+2,andthemolecularweightof14n+2,thecorrespondingparaffinbasegeneralformulaCnH2n+1,andthemolecularweightof14n+1,olefinsandnaphthenesgeneralformulaCnH2n,molecularweightof14n,thecorrespondingalkylthegeneralformulaCnH2n-1,themolecularweightof14n-1,alkynesandalkadienegeneralformulaCnH2n-2,molecularweightof14n2,correspondinghydroxylgeneralformulaCnH2n-3,themolecularweightof14n-3,socanbeknownmolecularweightminustheoxygen-containingfunctionalgroupsoftheorganicmattertypequantity,differencedividedby14(hydrocarbondirectlyinadditionto14),isoneofthelargestbusinessforthenumberofcarbonatoms(i.e.,thevalueofn),theremainderintothegeneralformula,andmolecularweightisofitsclass.
[example3]thetotalreactionofasinglechainofmonool14gramstoametalsodiumistogenerate0.2gramsofhydrogen.Theisomerofthisalcoholisthenumberofisomers
A.6B.7c.8d.9
Asoneyuanglycolcontainingonlyone-OH,permol,alcoholcanturnout1/2molh2,generatedbythe0.2gramsofH2infer14gramsofalcoholshouldbe0.2mol,sothemolecularweightof72grams/mo,themolecularweightof72,afterdeductingamountofhydroxytype17,remaining55,14,dividedbythebiggestdealerof3,13,isunreasonable,shouldtakebusinessfor4,to1,generationintothegeneralformula,andmolecularweightshouldbe4carbonolefinbaseornaphthenicbase,combinedwiththe"
linear"
soastodeducethenumberofisomersforsix.
2.Thisapproachismostsuitedtoqualitativelyaveragemethodisusedtosolvethecomponentsofthemixture,thepossibilityforthemixtureofingredients,withoutconsideringthecontentofeachcomponent.Accordingtothemixtureofvariousphysicalquantities(suchasdensity,volume,molecularweight,concentrationofamountofsubstance,suchasmassfraction),thedefinitionofthetypeorsubjecttoconditions,mixturecancalculatetheaverageofcertainphysicalquantities,buttheaveragemustbebetweencompositionmixturebetweenthevariouscomponentsofthesamephysicalquantityvalue,inotherwords,themixtureofthetwocomponentsofthephysicalquantitymustbealargerthanaverage,asmallerthanaverage,tomeettherequirements,whichcandeterminethemixtureofmay.
[example4]amixtureoftwometallicmonomixturesof13g,whichwereaddedtothefullamountofdilutesulfuricacid,emits11.2Lofgasinthestandardcondition.Thetwometalsmaybe
A.ZnandFeB.AlandZnC.AlandMgd.mgandCu
MixtureasAkindofmetal,becauseisadequatedilutesulphuricacid,13gramsofallmetalreactiongenerated11.2L(0.5mole)areallhydrogengas,thatis,themetalmust26gramsperrelease1molehydrogen,ifallis+2valencemetal,itsaverageatomicweightis26,compriseAmixtureof+2valencemetal,itsatomicweightAgreaterthan26,Asmallerthan26.Thegenerationofselecteditems,inreplacementofthehydrogenreaction,+2pricewithzinc,atomicweightis65,Featomicweightis56,Mgatomicweightof24,butforAl,becauseinthereaction+3valence,toreplacethe1molhydrogen,aslongas18gramsofAlisenough,canbeseenasA+2pricesitsatomicweightis27/(3/2)=18,ifhavetheNa+1pricetoparticipateinthesamereaction,itwillbeconsideredA+2pricewhenitsatomicweightis23*2=46,forCu,becauseitcan'
treplacetheH2,soastheatomicweightofinfinity,andgotanAinbothmetalatomicweightaremorethan26,Cintwokindsofmetalatomicweightarelessthan26,soA,doesnotmeettherequirements,CBAltheatomicweightofsmallerthan26,zincisgreaterthan26,DMginatomicweightissmallerthan26,Cuatomicweightisgreaterthan26,B,Dforthepersonstobetheanswer.
3.Limitmethod.Contrarylimitmethodandaveragemethod,thismethodisalsosuitableforthequalitativeorquantitativesolutionofmixturecomposition.Accordingtothemixtureofvariousphysicalquantities(suchasdensity,volume,molarmass,theamountofsubstanceconcentration,massfraction,etc.)thedefinitionofthetypeorsubjecttoconditions,themixtureasonlyoneofthecomponentA,namelythequalityscoreorgasvolumefractionis100%(maximum),anothercomponentBorcorrespondingtothemassfractionofgasvolumefractionis0%(minimum),canthevalueofoneofthecomponentsofAphysicalquantityN1,usingthesamemethodcanbecalculatedonlycontainBdoesnotcontainAmixtureofN2physicalquantitiesofthesamevalues,andthemixtureofthephysicalquantitiesNisaverage,mustbebetweenthemixtureofeachcomponentofA,B,betweenthesamequantityofnumericalnamelyN1<
N<
pingN2canmeettherequirements,whichcandeterminethemixtureofmay.
In[5]fourstudentsatthesametimeanalysisofamixtureofKClandKBr,theyallmatchintoaqueoussamplesfrom2.00grams,addenoughHNO3againafteraddingsuitableamountofAgNO3solution,afterbeingprecipitatedcompletelyfiltertogetthequalityoftheprecipitationofsilverhalidedryasshowninthefollowingfouroptions,ofwhichdataisreasonable
C.a.b.3.06g3.36g3.66gD.3.96
Subjectsuchasaccordingtothemethod,usuallymixturecontainingKClandKBr,canhaveaninfinitevarietyofways,thecalculateddataalsohasmanypossibilities,toverifythatthedataisreasonable,fouroptionsmustbeplugintoseeifthereisasolution,alsoisequivalenttofourquestionstodothemath,verymuch.Ittakestimetouselimitmethod,allsetto2.00gforKCl,accordingtoKCl-AgCl,every74.5gramsofKClcangenerate143.5gramsofAgCl,precipitationisavailablefor(2.00/74.5)*143.5=3.852grams,tothemaximum,thesamecanbeobtainedwhenthemixtureallforKBr,every119gramsofKBravailable