Definice krtka
Basicparticlesshouldbespecifiedwhenusingmol,whichcanbeatoms,molecules,ions,groupsofatoms,electrons,protons,neutronsandotherparticles,Oraspecificcombinationoftheseparticles.Accordingtointernationalregulations,thenumberofparticlescontainedin1molofparticlesis6.02×10²³,andthenumberofcarbonatomscontainedin0.012kg¹²C(carbon-12)isalsoequalto6.02×10²³.Therefore,onemoleofmattercontainsstructuralparticles.Thenumberofisequaltothenumberofatomscontainedin0.012kg¹²C(carbon12).
Sometimes,themassofonemoleofasubstanceiscalledthemolarmassofthesubstance,whichisrepresentedbythesymbolM,suchasM=2.02×10⁻³kgforhydrogenH2.ForasubstancewhosemassFisM,theratioofMtoμiscalledtheamountofthesubstance(alsoknownasthenumberofmoles),=Mμ.Forexample,M=4.04×10⁻³kgThenumberofmolesofhydrogenH₂=2.ThevolumeVmoccupiedbyonemoleofsubstanceiscalledthemolarvolume.Themolarvolumeofgasdependsontemperatureandpressure.Understandardconditions,theidealgasVm=22.41410L.Fmol⁻¹.Themolarvolumeofsolidandliquidsubstanceshasasmallrelationshipwithtemperatureandpressure.Thevolumeofamoleofdifferentsolidsubstancesanddifferentliquidsubstancesisdifferent.
Podle přesného měření vědeckých experimentů je známo, že 0,012 kg karbonatomu¹²C(uhlík-12) obsahuje asi 6,02×10²³.
Proč používat "12 gramů" a "uhlík¹²C (uhlík-12)" k definování molu? Hlavní důvody jsou následující (pouze pro středoškolské vzdělávání):
Whydoyouhaveto12grams?Becauseitsnucleuscontainsequalnumbersofneutronsandprotons.Whycanthenumberofneutronsandprotonsbeequaltoeachotherasthereferenceatomforthenumberofmoles?Becauseaneutronhasonemorenegativeelectronandsomeradiationthanaproton,strictlyspeaking,asingleneutronhasaslightlyhighermassthanaproton[itsmassis1.6749286×10⁻²⁷kg(939.56563MeV),whichisslightlyhigherthanthemassofaproton.Large(themassoftheprotonis1.672621637(83)×10⁻²⁷kg)scientificcountingistoocomplicated],inordertofacilitatethemeasurementofthemassofothernuclei,itisnecessarytotakeanintermediatevalueoftheneutronmassandtheprotonmass(theaveragevalueistraditionalMeasurementmethods).Then¹²C(carbon-12)nucleusisthebestchoiceasareferencebenchmark,anditexistsmorecommonlyanditspropertiesarerelativelystable.Inthisway,onetwelfthofthemassofthe¹²C(carbon12)nucleusisscientificallytheclosesttothemassofaneutronorproton.
Acertainnumber(Avogadro'sconstant,oronemole)ofneutrons(protons-hereyoucanregardneutronsandprotonsasparticleswiththesamemass)isbasicallyequalto1gram,thenThenucleusofonemoleofXelement[containingm(naturalnumber)protonsandn(naturalnumber)neutrons]ism+ngrams.Andm+nisexactlytheatomicweight.mdeterminesthepositionoftheatomintheperiodictableofelements,andndeterminestheatomicweightofatomsofthesameelement.
OnNovember16,2018,theInternationalConferenceonWeightsandMeasurespassedaresolutionthat1molewillbedefinedas"theamountofmatterinasystemcontainingexactly6.02214076×10²³basicunitssuchasatomsormolecules".Atthesametime,theAvogadroconstantwasrevisedto6.02214076×10²³.
Základní informace
Z vědeckého hlediska je agregát obsahující 6,02×10²³částic považován za jednotku zvanou krtek, což je jednotka, která představuje množství hmoty (symbolisn).
1 mol uhlíkového prvku obsahuje 6,02 × 10²³ uhlíků a hmotnost 12 gramů.
1molofelementalsulfurcontains6.02×10²³sulfuratomsandthemassis32grams.
Similarly,themassof1moleofanysubstanceisingrams,andthevalueisequaltotherelativeatomicmassorrelativemolecularmassofthatkindofatom(afixedvalue).
Vzorcová hmotnost (relativní molekulová hmotnost) vody je 18 a hmotnost 1 mol molekuly vody je 18 g, obsahující 6,02 × 10²3 molekul vody.
Obvykle se hmotnost 1 mol látky nazývá molární hmotnost látky (symbol M), jednotka molarmasgramů/mol, vyslovuje se jako "grampermol" (symboly "g/mol") Například, molarma vody je 18 g/mol, psané jako M(H₂O)=18g
Jaký je vztah mezi nimi jako látka (m), množstvím látky (n) a molární hmotností (M) látky?
To znamená: n=m/M,m=n×M,M=m/n
Generalformula:n(amountofmatter)=N(numberofparticles)/NA(Avogadroconstant)=m(mass)/M(molarmass)=V(gasvolume)/Vm(molarvolume:gasinSTP(standardcondition:273K(0℃)101KPa)1molgasvolumeis22.4L)=C(substanceconcentration)×V(totalvolumeofsolution)
Způsob zápisu: koeficient+mol+chemický vzorec (nebo čínské znaky, poznámka: čínské znaky)Musíte uvést, zda se jedná o molekulu nebo anatom atd.)
Forexample:onemoleofwatermoleculecanbewrittenas1molH₂Oor1molwatermolecule
Historie vývoje
InOctober1971,the14thInternationalConferenceonWeightsandMeasures,attendedby41countries,decidedtoaddtheseventhbasicunitoftheInternationalSystemofUnits(SI).Molarisusedtocalculatethenumberofparticles,themassofmatter,thevolumeofgas,theconcentrationofthesolution,theheatchangeofthereactionprocess,andsoon.MolecomesfromtheLatinmoles,whichoriginallymeansalotandaccumulation.
Thedefinitionofmoleinthe14thInternationalConferenceonWeightsandMeasuresin1971hasthefollowingtwoparagraphs:"Moleistheamountofsubstanceinasystem,andthenumberofbasicunitscontainedinthesystemisequalto0.012kgofcarbon-Thenumberofatomsof12isequal.""Whenusingmoles,thebasicunitshouldbespecified.Itcanbeatoms,molecules,ions,electronsandotherparticles,oraspecificcombinationoftheseparticles."Thetwoparagraphsaboveshouldberegardedasoneoverall.Thenumberofcarbonatomscontainedin0.012kgofcarbon-12nuclideistheAvogadroconstant(NA),andtheapproximatevaluemeasuredbytheexperimentisNA=6.02×10²³.Moleisdifferentfromgeneralunits.Ithastwocharacteristics:①Theobjectofmeasurementismicroscopicbasicunits,suchasmolecules,ions,etc.,anditcannotbeusedtomeasuremacroscopicsubstances.②ItusesAvogadro'snumberastheunitofmeasurement,whichisabatch,notthenumberofmolecules,atomsandotherparticles.Itcanalsobeusedtomeasurespecificcombinationsofmicroscopicparticles.Forexample,theamountofsulfuricacidismeasuredinmoles,thatis,1molofsulfuricacidcontains6.02×10²³sulfuricacidmolecules.Moleisthemostwidelyusedunitofmeasurementinchemistry.Forexample,itisusedinthecalculationofchemicalreactionequations,calculationinsolution,solutionpreparationanddilution,calculationofchemicalequilibrium,gasmolarvolume,andthermochemistry.basicunit.
Molarextinctioncoefficient,Molarabsorptioncoefficient,Molarabsorptioncoefficient
Spectrophotometryisbasedontheselectiveabsorptionofelectromagneticradiationbysubstanceswithdifferentmolecularstructures.Theestablishedmethodbelongstomolecularabsorptionspectrumanalysis.Whenlightpassesthroughthesolution,themeasuredsubstancemoleculesabsorbacertainwavelengthofmonochromaticlight,andtheintensityoftheabsorbedlightisproportionaltothedistancethelightpasses.AlthoughitisunderstoodthatBouguerhadproposedthemathematicalexpressionoftheaboverelationshipasearlyas1729,itisgenerallybelievedthatLambertfirstdiscoveredtheexpressionin1760,anditsmathematicalformis:
T=I/I0=10(-kb)
kdeI0jeintenzita dopadajícího světla,Ijeintenzita procházejícího světla,10(-kb)jeindex založený na 10,k je konstanta,bistheoptická délka dráhy (obvykle vyjádřená v cm).
Pivo je ekvivalentní s Bouguerovým salátem, ale Beer's je vyjádřeno mezikoncentracemi.
T=I/I0=10(-kb)
wherecistheconcentrationofthelight-absorbingsubstance(usuallyexpresseding/Lormg/Lastheunit).Aftertakingthelogarithmwiththebase10astheaboveformula,alinearexpressionisobtained:
A=-logT=-log(I/I0)=log(I0/I)=ebc
whereAistheabsorbanceandεisthemolarabsorptioncoefficientorextinctioncoefficient.
TheaboveexpressionisusuallycalledBeer'slaw.Itshowsthatwhenmonochromaticlightofaspecificwavelengthpassesthroughthesolution,theabsorbanceofthesampleisproportionaltotheconcentrationoftheabsorberinthesolutionandthedistancethelightpasses.
Whenthewavelength,solutionandtemperaturearedetermined,themolarextinctioncoefficientisdeterminedbythecharacteristicsofagivensubstance.Infact,themeasuredmolarextinctioncoefficientisalsorelatedtotheinstrumentused.Therefore,inquantitativeanalysis,themolarextinctioncoefficientofaknownsubstanceisusuallynotused,butoneormoreknownconcentrationsofthesubstancetobetestedareusedasacalibrationorworkingcurve.
Absorpční koeficient
Matematická exprese Beer's slawisA=kbc, je-li koncentrace roztoku cising/L,bisoptická dráha vcm, pak se konstanta K nazývá koeficient absorbance, vyjádřený a,a sunitilitr/(g·cm)[L/(g·cm],A=kbcc může být zapsáno.A.
IntheformulaA=kbcIs1mol/L,bis1cm,thenthecoefficientkiscalledmolarabsorptioncoefficient,expressedbyε,theunitisliters/(mol·cm)[L/(mol·cm)],A=kbccanbewrittenasA=εc.Inactualwork,youcannotdirectlymeasuretheabsorbancewithahigh-concentrationsolutionsuchas1mol/L,butcalculatetheabsorbancewhendilutedtoanappropriateconcentration.Theεvalueisrelatedtofactorssuchasthewavelengthoftheincidentlightandthenatureofthesolution.TheεofNADHat260nmis15000,whichiswrittenasε260NADH =15×10³;sat340nmis6220,který je zapsán jakoε340NADH=6,22×10³.
Forexample,cintheformulaA=kbcisthepercentageconcentration(w/v)biscm,thentheconstantkcanbeexpressedbyE%,whichiscalledthespecificabsorptioncoefficientorthepercentageabsorptioncoefficient,A=kbccanbewrittenasA=E%bc.Whenthechemicalstructureoftheanalyteisknown,εcanbeusedForvalueanalysis,ifthechemicalstructureofthetestsubstanceisunknown,εcannotbedetermined.Atthistime,itisveryconvenienttousethespecificabsorptioncoefficienttoanalyze.a,εandEareoftenusedforroughquantitativeanalysis,mainlyforqualitativeanalysis.
Chemická rovnice
Chemická rovnicecanexpresstheratiooftheamountofthesubstancebetweenthereactantandtheproductandtheratioofthemass.
Příklad: 2H2+02=(zapálit)=2H20
Poměr koeficientu je 2:1:2
Poměr počtu částic 2:1:2
Poměr množství látky 2:1:2
Hmotnostní poměr 4:32:36
Fromtheaboveanalysis,itcanbeseenthattheratioofthecoefficientsofeachsubstanceinthechemicalequationistheratiooftheamountofsubstancesbetweenthem.UsethisTheprinciplecanbebasedonthechemicalequationtocalculatetheamountofeachsubstance.
Onetwelfthofthemassofacarbonatom(¹²C)istheinternationalbenchmarkforrelativeatomicmass(formulaweight).Itisknownthat12g¹²Ccontains6.02214076×10²³carbonatoms.ThisnumberiscalledAvogadro'snumber,soitcanalsobesaidthattheamountofasubstancecontainingseveralbasicparticlesofAvogadrois1mol.Forexample,1molofoxygencontains6.02214076×10²³oxygenmolecules,itsmassis31.9988g.1molhydrogenioncontains6.02214076×10²³hydrogenions,anditsmassis1.00794g.Inthechemicalcalculation,theapproximatevalueis6.02×10²³ .