化工专业英语课件3.ppt

Analyticalchemistry,2020/5/24,1,IntroductiontoAnalyticalChemistry,2,2020/5/24,3,2020/5/24,Analyticalchemistryinvolvesseparating,identifying,anddeterminingtherelativeamountsofthecomponentsmakingupasampleofmatter.分析化学包括样品分离、定性以及确定组成成分的相对含量三方面内容。Qualitativeanalysisrevealsthechemicalidentityoftheanalytes.定性分析是确定被分析物(待测物)的化学组成。,4,2020/5/24,Quantitativeanalysistellsustherelativeamountsofoneormoreoftheseanalytesinnumericalterms.定量分析是确定一种或多种不同形式的被分析物的相对含量。Qualitativeinformationisrequiredbeforeaquantitativeanalysiscanbeundertaken.在进行定量分析之前需要先进行定性分析。Aseparationstepisusuallyanecessarypartofbothqualitativeandqualitativeanalysis.通常情况下，样品的预先分离是进行定性和定量分析之前必不可少的步骤。,Theroleofanalyticalchemistryinthescience,Analyticalchemistry,ortheartofrecognizingdifferentsubstancesanddeterminedtheirconstituents,takesaprominentpositionamongtheapplicationsofscience,sincethequestionswhichitenablesustoanswerarisewheneverchemicalprocessesareemployedforscientificortechnicalpurpose.分析化学是一门确定不同物质组成及其含量的学科，在科学应用中处于主导地位。这是由于分析化学可以帮助我们解决所有利用化工能解决的科学和技术所产生的问题。,5,2020/5/24,Itssupremeimportancehascausedittobeassiduouslycultivatedfromaveryearlyperiodinthehistoryofchemistry,anditsrecordscomprisealargepartofthequantitativeworkwhichisspreadoverthewholedomainofscience.分析化学的重要性使其在化学历史的最初期就得到了全面发展，同时分析化学记录包含了大部分的定量分析工作，并在整个科学领域得到广泛传播。,6,2020/5/24,Quantitativeanalyticalmeasurementalsoplayavitalroleinmanyresearchareasinchemistry,biochemistry,biology,geology,andtheothersciences.定量分析测量也在化学、生物化学、生物学、地理学以及其他科学的许多研究领域扮演者重要的角色。,7,2020/5/24,Forexample,chemistsunravelthemechanismsofchemicalreactionsthroughreaction-ratestudies,therateatwhichreactantsareconsumedorproductsformedinachemicalreactioncanbecalculatedfromquantitativemeasurementsmadeatequaltimeintervals.比如，化学家通过研究反应速率来阐明化学反应机理。而化学反应中反应物的消耗速率或产物的生成速率可以通过在相同时间间隔下进行定量测计算得到。,8,2020/5/24,Quantitativeanalysisforpotassium,calcium,andsodiumionsinthebodyfluidsofanimalspermitphysiologiststostudytheroletheseionsplayinnerve-signalconductionandmusclecontractionandrelaxation.生理学家通过对动物体液内钾离子、钙离子和钠离子的定量分析，来研究这些离子在神经信号传导和肌肉收缩和松弛中的作用。,9,2020/5/24,Materialsscientistsrelyheavilyuponquantitativeanalysisofcrystallinegermaniumandsiliconintheirstudiesofthebehaviorofsemiconductordevices.材料学家主要依赖对晶体锗和硅的定量分析来研究他们作为半导体元件的性能。Impuritiesinthesedevicesareintheconcentrationsrange1*10-6to1*10-10percent.这些元件中的杂质含量在百分之1*10-6到1*10-10的范围内。,10,2020/5/24,Archaeologistsidentifythesourceofvolcanicglassesbymeasuringtheconcentrationsofminorelementsinsamplestakenfromvariouslocations.考古学家通过测量从不同位置采集的样品中的微量元素的浓度来确定火山玻璃岩的来源。Thisknowledgeinturnmakesitpossibletotraceprehistorictraderoutesfortoolsandweaponsfashionedfromobsidian.以此类推，这种方法也有望用于史前流行的黑曜石工具和武器的交易路线的追踪研究。,11,2020/5/24,Aclassificationofquantitativemethodsofanalysis,Wecomputetheresultsofatypicalquantitativeanalysisfromtwoproductiveamountsofthecomponentsmakingupasampleofmatter.典型的定量分析结果是通过计算组成样品的两种大量成分的含量得到的。Qualitativeanalysisrevealsthechemicalmeasurements.定性分析是指化学测量。,12,2020/5/24,Oneistheweightorvolumeofsampletobeanalyzed.第一步是分析样品的重量或体积。Thesecondisthemeasurementofsomequantitythatisproportionaltotheamountofanalyteinthatsample.第二步是测量与样品中被分析物相当的物质的量。Thissecondsstepnormallycompletestheanalysis.第二步通常是完成分析的步骤。,13,2020/5/24,Chemistsclassifyanalyticalmethodsaccordingtothenatureofthisfinalmeasurement.化学家根据最后一步测量的性质对分析方法进行分类。Inagravimetricmethod,themassoftheanalyteorofsomecompoundschemicallyrelatedtoitisdetermined.重量分析法是用来确定被分析物或其他一些化学相关的物质的质量。,14,2020/5/24,Inavolumetricmethod,thevolumeofasolutioncontainingsufficientreagenttoreactcompletelywiththeanalyzerismeasured.容量法是指用含有过量试剂的溶液与被分析物完全反应，并测量反应的溶液的体积的方法。Electro-analyticalmethodsinvolvethemeasurementofsuchelectricalpropertiesaspotential,current,resistance,andquantityofelectricity.电化学分析法是测量电化学性质的方法，如测量电压、电流、电阻及电量等。,15,2020/5/24,Spectroscopicmethodsarebaseduponmeasurementsoftheinteractionbetweenelectromagneticradiationandanalyteatomsormoleculesorupontheproductionofsuchradiationbyanalytes.光谱分析法是基于测量被分析物原子或分子与电磁辐射之间的相互作用，或测量被分析物产生的辐射的方法。Finally,agroupofmiscellaneousmethodsshouldbementioned.最后，还应介绍一组不同种类的分析方法。,16,2020/5/24,Theseincludethemeasurementofsuchpropertiesasmass-to-chargeratio(massspectrometry),rateofradioactivedecay,heatofreaction,rateofreaction,thermalconductivity,opticalactivity,andrefractiveindex.这些分析方法测量被分析物的一些其他性质，包括荷质比（质谱），放射性衰变速率，反应热、反应速率、导热性、光学活性（旋光度）以及折射率。,17,2020/5/24,Stepinatypicalquantitativeanalysis,SelectingamethodSelectingwhichmethodtousetosolveananalyticalproblemisavitalfirststepinanyquantitativeanalysis.在任何定量分析中选择分析方法是解决问题至关重要的第一步。Thechoiceissometimesdifficult,animportantconsiderationinselectionistheaccuracyrequired.有时很难选择到合适的分析方法，其中一个至关重要的考虑因素就是分析对精确度的要求。,18,2020/5/24,Unfortunately,highreliabilitynearlyalwaysrequiredalargeinvestmentoftime.但是，要获得高可信度一般需要花费大量的时间进行分析。Thechosenmethodismostoftenacompromisebetweenaccuracyandeconomics.分析方法的选择往往是综合考虑了精确度和经济性两方面因素。,19,2020/5/24,SamplingToproducemeaningfulinformation,ananalysismustbeperformedonasamplewhosecompositionfaithfullyrepresentsthatofthebulkofmaterialfromwhichthesamplewastaken.为了获得有价值的信息，分析所使用的样品必须能够如实地代表大部分被分析物的组成。Wherethebulkislargeandinhomogeneous,greateffortisrequiredtogetarepresentativesample.当待测物质是体积庞大并且组成不均匀的样品时，想要获得具有代表性的样品并不容易。,20,2020/5/24,Consider,forexample,arailroadcarcontaining25tonsofsilverore.例如，试想有一辆装有15吨银矿石的有轨电车。Buyerandsellermustagreeonthevalueoftheshipmentbasedprimarilyitssilvercontent.买家和卖家对这批货物的价值达成共识，主要是依据货物中银的含量。Theoreisinherentlyheterogeneous,consistingofproductiveamountsofthecomponentsmakingupasampleofmatter.矿石是内部均匀的，由大量的组分构成的样品。,21,2020/5/24,PreparingalaboratorysampleAftersampling,solidmaterialsfrequentlyaregroundtodecreaseparticlesize,mixedtoensurehomogently,andstoredforvariouslengthsoftimebeforetheanalysisbegins.取样后，固体材料通常需要研磨成更小的颗粒，并混合均匀，在分析之前需要进过不同时间的贮藏。Duringeachofthesesteps,absorptionordesorptionofwatermayoccur,dependinguponthehumidityoftheenvironment.在这些步骤中，可能会发生样品的吸水和脱水，这主要取决于环境的湿度。,22,2020/5/24,Becauseanylossorgainofwaterchangesthechemicalcompositionofasolid,itisagoodideatocarefullydrysamplesatthestartofananalysis.由于任何水分的缺失或获得都会引起固体样品化学组成的变化，因此，在对样品分析之前最好先进行严格的干燥处理。Alternatively,themoisturecontentofthesamplecanbedeterminedattimeoftheanalysisinaseparateanalyticalprocedure.另一种方法，样品中的水分含量可以在进行分析的同时，通过单独的分析步骤进行测定。,23,2020/5/24,DefiningreplicatesamplesMostchemicalanalysisareperformedonreplicatesampleswhoseweightorvolumeshavebeendeterminedbycarefulmeasurementwithananalyticalbalanceorwithaprecisevolumetricdevice.大部分的化学分析都是在随机抽样样品上进行的，这些样品的重量和体积已经通过分析天平或精密体积测量设备测量给出。Obtainingreplicatedataonsamplesimprovesthequalityoftheresultsandprovidesameasureoftheirreliability.样品随机抽样数据的获得提高了分析结果的质量，并可以测验其分析的可信度。,24,2020/5/24,PreparesolutionofthesampleMostanalysisareperformedonsolutionofthesample.大多数的分析都是针对溶液样品进行的。Ideally,thesolventshoulddissolvetheentiresamplerapidly.最理想的情况是样品可以在溶剂中快速完全溶解。Theconditionsofdissolutionshouldbesufficientmildsothatlossoftheanalytecannotoccur.应尽量避免待测物质的分解，以减少由此造成的损失。,25,2020/5/24,Unfortunately,manymaterialsthatmustbeanalyzedareinsolubleincommonsolvents.但是，许多需要分析的待测物质在常规溶剂中很难溶解。Examplesincludesilicateminerals,high-molecule-weightpolymers,andspecimensofanimaltissue.这些物质包括硅矿石，高聚物以及动物组织标本。Conversionoftheanalyteinsuchmaterialstobeasolubleformcanbeadifficultandtime-consumingtask.将上述物质转变成可溶物形式进行分析，是一项极其困难又耗时的工作。,26,2020/5/24,CalibrationanmeasurementQualitativeanalysisrevealsthechemicalmanylumpsthatvaryinsizeaswellasinsilvercontent.定性分析是分析许多不同尺寸及银含量的化学块状物。Theanalysistohavesignificance,thissmallsamplemusthaveacompositionthatisrepresentativeofthe25tonsoreintheshipment.这种小的样品必须能够代表这批25吨银矿石货物的组成，这样定性分析才有意义。,27,2020/5/24,Thetaskistoisolate1gofmaterialthataccuratelyreflectstheaveragecompositionofthenearly23000000gbulksample.取样工作就是从待分析物中取出1g样品，并使其可以充分代表将近23000000g样品的平均组成。Obtainingsucharepresentativesampleisadifficultundertakingthatrequiresacareful,systematicmanipulationoftheentireshipment.要想获得这样具有代表性的样品相当不容易，它需要对整个样品进行仔细的，系统的处理。,28,2020/5/24,Acidsandbases,Keytheory:Bronsted-Lowrytheoryofacidsandbases:Acid-basereactionsareonesinwhichprotonsaregivenandtaken.Acidsareprotondonors,basesareprotonacceptors.,29,2020/5/24,HF+H2OH3O+F,H2O+NH3NH4+OH,AcidbaseConjugateConjugateacidbase,tobeabletogiveprotons,andacidmusthaveahydrogenatomwhichcanbelost.,tobeabase,asubstancemusthavealonepairwhichcanbecomeasigmapairasitacceptsaproton.,Conjugatepairs,Everyacidhaswhatiscalledaconjugatebase.Thisistheparticleleftwhentheacidhasgivenawayitsproton.Inthesameway,everybasehasaconjugateacid,whichistheparticlemadewhenprotonhasarrived.SotheconjugatebaseofHClisCl-andtheconjugateacidofammoniaisNH4+.Familiarconjugatepairs:,30,2020/5/24,Ampholytes,Thewaterinthefirstreactionaboveisactingasabase,oneofitslonepairsacceptsaprotons.Inthesecondreactionthewaterisbeinganacid,givingoneofitsprotonstoammonia.Substanceslikewater,withhydrogensthatcanbelostandlonepairsthatcanbeprotoned,arecalledampholytes.Theycanbeeitheracidsorbasesdependingonwhattheyreactwith.,31,2020/5/24,HF+H2OH3O+F,H2O+NH3NH4+OH,Exercise,Whicharetheconjugatepairsinthebelow?,32,2020/5/24,NH3、OH、Na+、NH2、NH4+、Cl、H+。,Isthereanyampholyte?,NH3,IndicatorsIndicatorsaresubstanceswhichchangecolourasthepHchanges.Anindicatorisaweakacidwhoseconjugatebaseisadifferentcolour.HInH3O+In-colourAcolourBInacidtherewillbealotofH3O+andsotheequilibriumwilllietotheleft.ThecolourseenwillbecolourA.Inalkalineconditions,alltheH3O+ionswillbeuesdupandtheequilibriumwillmovetotheright.ThecolourseenwillbecolourB.,33,2020/5/24,IndicatorsWhenthereareequalamountsofthetwocolours,HInwillequalIn-andthecolourwillbeamixtureofAandB.ThishappenswhenpH=pKHInasshownbelow.1HIn=In-,sopH=pKHInThesuddenchangeincolourseeninatitrationiscalledtheend-point.Somepeoplearecolourblind,butmostpeoplecandetectachangeincolourwhentheratioofAtoBis1:10or10:1.ThismeansmostindicatorshaveausefulpHchangerangeofabout2pHunits.,34,2020/5/24,Equivalencepoint,Theequivalencepointofthetitration,whenamountsofacidandbaseexactlybalance,andtheendpointwillbeveryclosetoeachotherifthecorrectindicatorhasbeenchosen.,35,2020/5/24,Indicatorstructure,Indicatorstructurearequitecomplicatedmoleculeswhoseelectronicstructurechangesastheyareprotonatedordeprotonated.Thischangeinelectronicstructureresultsinachangeinelectronicenergylevelsandsoachangeincolour.,36,2020/5/24,37,2020/5/24,38,2020/5/24,MethylorangeMOMethylredMRPhenolphthaleinPP,Buffersolutions,BuffersolutionsresistchangesinpHonadditionofacidoralkali.BuffersolutionstendtoresistchangesinpHwhensmallamountsofacidorbaseareaddedandtheirpHisnotaffectedbydilution.,39,2020/5/24,Buffersolutions,Acidbuffersaremadeofasolutionofaweakacidanditsconjugatebase,e.g.asolutionofethanoicacidandsodiumethanoate.Basicbuffersaremadeofasolutionofaweakbaseanditsconjugateacid,e.g.asolutionofammoniaandammoniumchloride.,40,2020/5/24,Howbufferswork?,Wehaveseenthatabuffercontainsparticleswhichcanreactwitheitheranyacidoranybasewhichisadded.,41,2020/5/24,CH3COOH+H2OCH3COO-+H3O+,Lotsofspareacidmoleculesbecauseethanoicacidisaweakacid.,Lotsofspareconjugatebasebecausesodiumethanoatehasbeenaddedtotheacidsolution.,Additionofabase,Anybasethatisaddedreactswiththehydroxoniumions,H3O+,andusesthemup.Thismeansthatt