Myyrän määritelmä
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.
Tieteellisten kokeiden tarkan mittauksen mukaan tiedetään, että 0,012 kilohiiliatomia¹²C(hiili-12) sisältää noin 6,02 × 10²³.
Miksi käyttää "12 grammaa" ja "hiili¹²C(hiili-12)" määritelläkseen?
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.
Perustiedot
Tieteellisesti 6,02 × 10²³ hiukkasia sisältävää aggregaattia pidetään yksikkönä, nimeltään mooli, joka on aineen määrää edustava yksikkö (symboli). Lyhennettynä asmol, yksikkösymbolismi.
1 moolihiilielementti sisältää 6,02 × 10²³ hiiliatomia ja massa 12 grammaa.
1molofelementalsulfurcontains6.02×10²³sulfuratomsandthemassis32grams.
Similarly,themassof1moleofanysubstanceisingrams,andthevalueisequaltotherelativeatomicmassorrelativemolecularmassofthatkindofatom(afixedvalue).
Veden kaavapaino (suhteellinen molekyylimassa) on 18 ja 1 molvesimolekyylin massa on 18 g, joka sisältää 6,02 × 10²³ vesimolekyylejä.
Yleensä 1moolimassaa kutsutaan aineen moolimassaksi (symboliM),moolimassayksiköksigrammaa/mol, lausutaan "g/mol"(symboli"g/mol")Esimerkiksi,veden molaarinen massa on18g/mol,kirjoitettunaM(H₂O)=18g/mol.
Mikä on aineen massan (m), aineen määrän (n) ja aineen molaarimassan (M) välinen suhde?
Eli: 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)
Kirjoitustapa:kerroin+mooli+kemiallinen kaava(tai kiinalaiset merkit, huomautus:kiinalaiset merkit) on ilmoitettava, onko kyseessä amolekuleoranatomi jne.)
Forexample:onemoleofwatermoleculecanbewrittenas1molH₂Oor1molwatermolecule
Kehityshistoria
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(-kt)
jossaI0ontapahtumavalon intensiteetti,Ionläpäisevän valon intensiteetti,10(-kb)on indeksi, joka perustuu 10:een,kisavakioon,bisteoptiseen polunpituuteen (yleensä ilmaistuna cm).
Olut on lainmukaisesti sama kuin Bouguer'slaw, mutta olut on ilmaistu tiivistysväliin. Yhdistämällä nämä lait muodostaa Beer-Bouguerlaw:
T=I/I0=10(-kt)
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.
Absorptiokerroin
Beer'slawis:n matemaattinen ilmaisuA=kbc,josliuoksen pitoisuus/L,bisteoptinen polkucm,vakioKkutsutaanabsorbanssikerroin,ilmaistuna,ja yksikkölitra/(g·cm)[L/(g·cm],A=kbccanbewrit.
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;theεat340nmis6220,joka on kirjoitettunaε340NADH=6,22×10³.
Forexample,cintheformulaA=kbcisthepercentageconcentration(w/v)biscm,thentheconstantkcanbeexpressedbyE%,whichiscalledthespecificabsorptioncoefficientorthepercentageabsorptioncoefficient,A=kbccanbewrittenasA=E%bc.Whenthechemicalstructureoftheanalyteisknown,εcanbeusedForvalueanalysis,ifthechemicalstructureofthetestsubstanceisunknown,εcannotbedetermined.Atthistime,itisveryconvenienttousethespecificabsorptioncoefficienttoanalyze.a,εandEareoftenusedforroughquantitativeanalysis,mainlyforqualitativeanalysis.
Kemiallinen yhtälö
Kemiallinen yhtälöcanexpresstheratiooftheamountofthesubstancebetweenthereactantandtheproductandtheratioofthemass.
Esimerkki: 2H2+O2=(sytytä)=2H2O
Kertoimien suhde 2:1:2
Hiukkasten lukumäärän suhde 2:1:2
Aineen määrän suhde 2:1:2
Painosuhde 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 .