第二十四章容量

Lesson24.VolumetricAnalysis学习词汇常用的化学实验仪器3.练习全文翻译容量分析volumetric体积的，容量的unknowntestsample未知试样coincide符合，一致stoichiometric化学计量的endpoint终点titration滴定molarity摩尔浓度normality当量浓度equivalent当量grammolecularweight克分子量moleweight分子量curve曲线graph曲线图representation代表，象征marking刻度，条纹，标志burette滴定管tapwater自来水rinse冲洗drain依次排出vinegar醋methylred甲基红record记录pHmeterpH计frost霜，霜化render致使，使成为simultaneously同时地inthecaseof在…情况下，要是bringabout导致，引起1.学习词汇mol(e)-摩尔，分子

molarityn.摩尔浓度

moleculen.分子

molecularadj.分子的nor-正，正常，降，去甲

normaladj.正常的，普通的

normalizev.使正常化

normalityn.当量浓度

norbornenen.降冰片烯

noradrenalinen.去甲肾上腺素前后缀坩埚crucible2.常用的化学实验仪器蒸发皿evaporationdish三脚架tripod泥三角Claytrianglebeaker烧瓶圆底烧瓶平底烧瓶roundbottomflaskflatbottomflaskFlorenceflask烧瓶两口烧瓶2-neckBoilingflask集气瓶gas-jarAlcohol

burnerwiregauzegas-jarroundbottomflaskStopperStopperRingstandwithring广口瓶Widemouthbottle滴瓶Dropping

bottle

温度计100mL10mL量筒

Thermometergraduated

cylinderMeasuringcylinder注意区别BuretteAcidburetteBaseburette容量瓶容量瓶volumetricflaskBuretteclampBurettestandAcidburetteBaseburetteBurettestandwithdoubleclampsHoldingtwoburettevolumetricflaskErlenmeyerflaskConicalflask分液漏斗separatingfunnelBuchnerfunnelAllihntypecondenserWesttypecondenserserpentinecondenseradapterDistillingheadTesttubeTesttuberackTesttubebrushtesttubeclamppipettepipettetriangularflaskPlasticsqueezebottleRubberpipettebulb3.练习全文翻译Chemicalanalysescanbemadebydetermininghowmuchofasolutionofknownconcentrationisneededtoreactfullywithanunknowntestsample.Themethodisgenerallyreferredtoasvolumetricanalysisandconsistsoftitratingtheunknownsolutionwiththeoneofknownconcentration(astandardsolution).Bytitration,youcandetermineexactlyhowmuchofareagentisrequiredtobringaboutcompletereactionofthetestsolution.化学分析的一般通过测定一已知浓度的溶液与未知试样完全反应的关系来进行，该方法一般也称为容量分析，方式是用已知浓度的标准溶液来滴定未知溶液。通过滴定分析，你可以测定与试样完全反应的标准溶液的消耗量。Generalprinciples

通用原理Usually,completionofthereactionisindicatedbyasudden,visiblechangeinthereactionsystemthatcoincideswiththestoichiometricrelationshipbetweenmolesorequivalentsof-thereagentsolutionandthereactantinthetestsolution.Adroportwoofanappropriateindicatorsolutionproducesacolorchangeatthepointwherethereactioniscomplete-referredtoastheendpoint.一般来说，反应体系出现可见的突变表明反应已完全进行，此时滴定剂与被滴定物质的摩尔数或当量满足一定的化学计量关系。1~2滴合适的指示剂可在某个时刻产生颜色突变，此时滴定反应完全进行，称为滴定终点。Molarityisthenumberofmoles(gram-molecularweights)ofsubstanceperliterofsolution.Themoleweightofsulfuricacidis98.08g,andtherefore,1moleofH2SO4contains98.08g.If49.04garedilutedto1literthentheconcentrationis0.49or0.5M.Inthecaseofhydrochloricacid,HCl,a1Msolutionispreparedbytaking36.465gofHC1anddilutingto1liter.Theprocedureisthesameforbases.摩尔浓度是每升溶液中含有某物质的摩尔数（或克分子量）。硫酸的克分子量为98.08g，因此1M的硫酸溶液含有98.08g的硫酸；如果49.04g的硫酸稀释到1L溶液，那硫酸的浓度为0.49或0.5M。以盐酸为例，1M盐酸由1MHCl溶于1L水制得，碱的情况亦是如此。Normalityisthenumberofequivalentweightsofsubstanceperliterofsolution.Theequivalentweightofanacidistheweightofthatacidcapableoffurnishing1moleofprotons(H+),andtheequivalentweightofabaseistheweightofbasecapableofreceiving1moleofprotons.TheequivalentweightofH2SO4is98.08g/2or49.04g.Therefore,anormalsolution(N)ofH2SO4contains49.04gperliter.当量浓度是一升溶液中某物质的当量数，酸的当量指能提供1摩尔氢离子的酸的质量，碱的当量是接受1摩尔氢离子的碱的质量。硫酸的当量为98.08g除以2或49.04g，因此一当量的硫酸溶液每升含有49.04g硫酸。Thenormalityofanacidorbaseofunknownconcentrationmaybedeterminedbytitration.Theadvantageofusingnormalityratherthanmolarityisthatequalvolumesofsolutionsofequalnormalitieshaveidenticalcapacitiesforneutralization,becausetheycontainthesamenumberofequivalentweights.未知浓度的酸/碱的当量浓度可用滴定分析测定，当量浓度优于摩尔浓度在于相同体积的等当量溶液具有相同的中和能力，因为两者具有相同的当量数。Inatitration,wecompareequivalentweightsofacidandbase.Thenumberofequivalentsofacidisequaltotheproductofthevolumeoftheacidsolutionanditsnormality.Thenumberofequivalentsofbaseistheproductofthevolumeofthebasesolutionanditsnormality.Neutralizationhastakenplacewhenthenumberofequivalentsofacidisequaltothenumberofequivalentsofbase.滴定时我们会比较酸与碱的当量。酸的当量数等于酸的体积乘以它的当量浓度，碱的当量数等于碱的体积乘以当量浓度。当酸与碱的当量数相等时，中和反应发生。Caremustbeexercisedthroughoutthetitrationprocedure.Theburetteshouldbethoroughlycleanedwithsoapandwater,rinsedwithtapwater,andfinally,rinsedwithdistilledwater.Justbeforeuse,theburetteshouldberinsedwithtwo5-mlportionsofthesolutiontobeusedintheburette.Thisisdonebyholdingtheburetteinasemi-horizontalpositionandrollingthesolutionaroundtheentireinnersurface.Allowthefinalrinsingtodrainthroughthetip.滴定过程要十分小心，滴定管必须用肥皂和水完全洗净，再依次用自来水和蒸馏水冲洗。使用前滴定管还要用5-mL的使用溶液清洗两遍，其过程为：将滴定管半平放，转动滴定管使管内溶液与内表面充分浸润，然后从滴定管尖嘴放掉润洗溶液。Procedure

步骤Filltheburettetoapointabovethetopmarkingandallowthesolutiontorunoutuntilthebottomofthemeniscusisjustatthetopmarkingoftheburette.Theburettetipmustbecompletelyfilledtodeliverthevolumemeasured.在滴定管内引入溶液到高于顶端刻度线以上，然后从尖嘴处放出溶液直至凹液面与顶端刻线齐平，滴定管尖嘴要完全充满溶液以放出准确的体积。Inaddition,theburettemustbecleanedthoroughlyafterusebecausesodiumhydroxideandothertypesofsolutionswilleventuallyfrosttheglassandrenderanexpensivepieceofequipmentuseless.此外滴定管在使用后也要完全洗净，因为氢氧化钠和其它类型的试剂会腐蚀玻璃，导致滴定管的某个昂贵组件无法使用。1.TitrationofVinegarMeasure50mlofvinegarwithapipetteandpourintoa250-mlbeaker.Add2dropsofphenolphthaleinindicator.Fillaburettewitha1Nsolutionofsodiumhydroxide(NaOH)anddrawouttheexcessasdescribedabove.FromtheburetteaddNaOHtothebeakerofvinegaruntil1dropofNaOHproducesapalepinkcolorinthesolution.Maintainconstantstirring.Theappearanceofpinktellsyouthattheacidhasbeenneutralizedbythebaseandthereisnow1dropofexcessbasewhichhasturnedtheindicator.Readtheburetteandrecordthisreadingasthevolumeofbaseusedtoneutralizetheacid.

1.食醋的滴定：用吸液管量取50mL的食醋到250mL烧杯，加入两滴酚酞指示剂，将1当量的氢氧化钠浓度装入碱式滴定管，并按上述操作放出多余的溶液。从滴定管将氢氧化钠加入到烧杯与食醋反应，直至过量的一滴氢氧化钠使酚酞产生浅粉色，滴定过程中要一直振荡溶液。粉色的出现表明酸已完全被碱中和，过量的一滴氢氧化钠与指示剂反应使其变色。读出滴定管的刻度，记下中和食醋的氢氧化钠的体积。Accordingtotheequation：NaOH+CH3COOH→Na++CH3COO-+H2OOnemoleculeofNaOHneutralizesonemoleculeofaceticacid,oronegram-molecularweightofNaOHneutralizesonegram-molecularweightofaceticacid.Calculatetheamountofaceticacidpresentinthevinegar.Reportthisamountasthepercentageofaceticacid.根据反应式NaOH+CH3COOH→Na++CH3COO-+H2O，一分子氢氧化钠中和一分子的乙酸，或一克分子量的氢氧化钠中和一克分子量的乙酸。然后计算出醋中乙酸的含量，用乙酸的百分比来表示。2.StandardTitrationCurveIfapHmeterisavailable,repeattheaboveprocessusingapHmeterforconstantlydeterminingthepH.Whentheendpointisreached,continueaddingthebasetoexpandthecurvefurther.Makeagraphforthistitration.

2.标准滴定曲线：如果有一个pH计，重复上述滴定过程，同时用pH计测定体系的pH值，到达滴定终点后，继续滴加氢氧化钠并记录pH值，作一张（滴定剂消耗量vspH值的）滴定曲线图。3.EquivalentsofAcidUsingthe1NsolutionofNaOH,determinethenumberofequivalentsintwosamplesofbenzoicacid.Carryouttheprocedureforthetwodeterminationssimultaneously.Fromthisvaluecalculatetheequivalentweightoftheacid.Thesolidshouldbeweighedinabeakerandshouldbedissolvedinabout25mlofethylalcoholbeforetitrationwiththebase.Between2.0and2.2gofthesolidprovidethebestresults.Recordalldataandmakeallcalculationsnecessarytodeterminetheequivalentweightofthesolidacid.Compareyourexperimentalvaluewiththeequivalentweightofbenzoicacid(calculatedfromtheformula)anddeterminethepercentageoferrorofyourwork.

3.酸的当量：用一当量浓度的氢氧化钠，测定两个苯甲酸样品的当量数，