Определение на бенка
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.
Според прецизно измерване на научни експерименти е известно, че 0,012 kgfa въглероден атом¹²C(въглерод-12) съдържа около 6,02×10²³.
Защо да използвате "12 грама" и "въглерод¹²C(въглерод-12)", за да дефинирате мол? Основните причини са следните области (само за обучение в средното училище):
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.
Основна информация
Научно, агрегатът, съдържащ 6,02×10²³ частици, се разглежда като единица, наречена мол, която единица представлява количеството материя (символ). Съкратено като мол, единицата символ мол.
1 мол въглероден елемент съдържа 6,02 × 10²³ въглеродни атоми и маса 12 грама.
1molofelementalsulfurcontains6.02×10²³sulfuratomsandthemassis32grams.
Similarly,themassof1moleofanysubstanceisingrams,andthevalueisequaltotherelativeatomicmassorrelativemolecularmassofthatkindofatom(afixedvalue).
Формулното тегло (относителна молекулна маса) на водата е 18, а масата на 1 mol водна молекула е 18 g, съдържаща 6,02 × 10²³ водни молекули.
Обикновено масата на 1 мол вещество се нарича моларна маса на веществото (символ M), единицата за моларна маса грам/mol, произнася се като "грампермол" (символ "g/mol") Например, моларната маса на водата е 18 g/mol, записана като M(H₂O)=18 g/mol.
Каква е връзката между масата на веществото (m), количеството на веществото (n) и моларната маса (M) на веществото?
Това е: 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)
Метод на писане: коефициент+mol+химическа формула (или китайски йероглифи, забележка: китайски йероглифи) Трябва да се посочи дали е молекулно-оранатам и т.н.)
Forexample:onemoleofwatermoleculecanbewrittenas1molH₂Oor1molwatermolecule
История на развитието
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)
където I0 е интензитетът на падащата светлина, I е интензитетът на предадената светлина, 10(-kb) е индексът, базиран на 10,kisaконстанта,bistheopticalpathlength(обикновено изразена в cm).
Правото на бирата е еквивалентно на закона на Бугер, но правилото на Бирата изразява граници на концентрация. Комбинирайте двата закона, за да образувате закона на Бирата-Бугер:
T=I/I0=10(-kb)
wherecistheconcentrationofthelight-absorbingsubstance(usuallyexpresseding/Lormg/Lastheunit).Aftertakingthelogarithmwiththebase10astheaboveformula,alinearexpressionisobtained:
A=-logT=-log(I/I0)=log(I0/I)=εbc
whereAistheabsorbanceandεisthemolarabsorptioncoefficientorextinctioncoefficient.
TheaboveexpressionisusuallycalledBeer'slaw.Itshowsthatwhenmonochromaticlightofaspecificwavelengthpassesthroughthesolution,theabsorbanceofthesampleisproportionaltotheconcentrationoftheabsorberinthesolutionandthedistancethelightpasses.
Whenthewavelength,solutionandtemperaturearedetermined,themolarextinctioncoefficientisdeterminedbythecharacteristicsofagivensubstance.Infact,themeasuredmolarextinctioncoefficientisalsorelatedtotheinstrumentused.Therefore,inquantitativeanalysis,themolarextinctioncoefficientofaknownsubstanceisusuallynotused,butoneormoreknownconcentrationsofthesubstancetobetestedareusedasacalibrationorworkingcurve.
Коефициент на поглъщане
Математическият израз на slawi на Beer е A=kbc, ако концентрацията на разтвора е/L,bistheopticalpathincm,тогава константатаKсе нарича коефициент на поглъщане,изразен чрез a,и неговата единица литър/(g·cm)[L/(g·cm],A=kbccможе да бъде записан като A=abc.
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;εпри 340nmis6220,което е написано катоε340NADH=6,22×10³.
Forexample,cintheformulaA=kbcisthepercentageconcentration(w/v)biscm,thentheconstantkcanbeexpressedbyE%,whichiscalledthespecificabsorptioncoefficientorthepercentageabsorptioncoefficient,A=kbccanbewrittenasA=E%bc.Whenthechemicalstructureoftheanalyteisknown,εcanbeusedForvalueanalysis,ifthechemicalstructureofthetestsubstanceisunknown,εcannotbedetermined.Atthistime,itisveryconvenienttousethespecificabsorptioncoefficienttoanalyze.a,εandEareoftenusedforroughquantitativeanalysis,mainlyforqualitativeanalysis.
Химично уравнение
Химично уравнениеcanexpresstheratiooftheamountofthesubstancebetweenthereactantandtheproductandtheratioofthemass.
Например: 2H₂+O₂=(запалване)=2H2O
Съотношението на коефициентите е 2:1:2
Съотношение на броя на частиците 2:1:2
Съотношение на количеството на веществото 2:1:2
Масово съотношение 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 .