第二十四章容量

Lesson24.VolumetricAnalysis學習詞匯常用的化學實驗儀器3.練習全文翻譯容量分析volumetric體積的，容量的unknowntestsample未知試樣coincide符合，一致stoichiometric化學計量的endpoint終點titration滴定molarity摩爾濃度normality當量濃度equivalent當量grammolecularweight克分子量moleweight分子量curve曲線graph曲線圖representation代表，象征marking刻度，條紋，標志burette滴定管tapwater自來水rinse沖洗drain依次排出vinegar醋methylred甲基紅record記錄pHmeterpH計frost霜，霜化render致使，使成為simultaneously同時地inthecaseof在…情況下，要是bringabout導致，引起1.學習詞匯mol(e)-摩爾，分子

molarityn.摩爾濃度

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.當量濃度

norbornenen.降冰片烯

noradrenalinen.去甲腎上腺素前后綴坩堝crucible2.常用的化學實驗儀器蒸發(fā)皿evaporationdish三腳架tripod泥三角Claytrianglebeaker燒瓶圓底燒瓶平底燒瓶roundbottomflaskflatbottomflaskFlorenceflask燒瓶兩口燒瓶2-neckBoilingflask集氣瓶gas-jarAlcohol

burnerwiregauzegas-jarroundbottomflaskStopperStopperRingstandwithring廣口瓶Widemouthbottle滴瓶Dropping

bottle

溫度計100mL10mL量筒

Thermometergraduated

cylinderMeasuringcylinder注意區(qū)別BuretteAcidburetteBaseburette容量瓶容量瓶volumetricflaskBuretteclampBurettestandAcidburetteBaseburetteBurettestandwithdoubleclampsHoldingtwoburettevolumetricflaskErlenmeyerflaskConicalflask分液漏斗separatingfunnelBuchnerfunnelAllihntypecondenserWesttypecondenserserpentinecondenseradapterDistillingheadTesttubeTesttuberackTesttubebrushtesttubeclamppipettepipettetriangularflaskPlasticsqueezebottleRubberpipettebulb3.練習全文翻譯Chemicalanalysescanbemadebydetermininghowmuchofasolutionofknownconcentrationisneededtoreactfullywithanunknowntestsample.Themethodisgenerallyreferredtoasvolumetricanalysisandconsistsoftitratingtheunknownsolutionwiththeoneofknownconcentration(astandardsolution).Bytitration,youcandetermineexactlyhowmuchofareagentisrequiredtobringaboutcompletereactionofthetestsolution.化學分析的一般通過測定一已知濃度的溶液與未知試樣完全反應的關系來進行，該方法一般也稱為容量分析，方式是用已知濃度的標準溶液來滴定未知溶液。通過滴定分析，你可以測定與試樣完全反應的標準溶液的消耗量。Generalprinciples

通用原理Usually,completionofthereactionisindicatedbyasudden,visiblechangeinthereactionsystemthatcoincideswiththestoichiometricrelationshipbetweenmolesorequivalentsof-thereagentsolutionandthereactantinthetestsolution.Adroportwoofanappropriateindicatorsolutionproducesacolorchangeatthepointwherethereactioniscomplete-referredtoastheendpoint.一般來說，反應體系出現可見的突變表明反應已完全進行，此時滴定劑與被滴定物質的摩爾數或當量滿足一定的化學計量關系。1~2滴合適的指示劑可在某個時刻產生顏色突變，此時滴定反應完全進行，稱為滴定終點。Molarityisthenumberofmoles(gram-molecularweights)ofsubstanceperliterofsolution.Themoleweightofsulfuricacidis98.08g,andtherefore,1moleofH2SO4contains98.08g.If49.04garedilutedto1literthentheconcentrationis0.49or0.5M.Inthecaseofhydrochloricacid,HCl,a1Msolutionispreparedbytaking36.465gofHC1anddilutingto1liter.Theprocedureisthesameforbases.摩爾濃度是每升溶液中含有某物質的摩爾數（或克分子量）。硫酸的克分子量為98.08g，因此1M的硫酸溶液含有98.08g的硫酸；如果49.04g的硫酸稀釋到1L溶液，那硫酸的濃度為0.49或0.5M。以鹽酸為例，1M鹽酸由1MHCl溶于1L水制得，堿的情況亦是如此。Normalityisthenumberofequivalentweightsofsubstanceperliterofsolution.Theequivalentweightofanacidistheweightofthatacidcapableoffurnishing1moleofprotons(H+),andtheequivalentweightofabaseistheweightofbasecapableofreceiving1moleofprotons.TheequivalentweightofH2SO4is98.08g/2or49.04g.Therefore,anormalsolution(N)ofH2SO4contains49.04gperliter.當量濃度是一升溶液中某物質的當量數，酸的當量指能提供1摩爾氫離子的酸的質量，堿的當量是接受1摩爾氫離子的堿的質量。硫酸的當量為98.08g除以2或49.04g，因此一當量的硫酸溶液每升含有49.04g硫酸。Thenormalityofanacidorbaseofunknownconcentrationmaybedeterminedbytitration.Theadvantageofusingnormalityratherthanmolarityisthatequalvolumesofsolutionsofequalnormalitieshaveidenticalcapacitiesforneutralization,becausetheycontainthesamenumberofequivalentweights.未知濃度的酸/堿的當量濃度可用滴定分析測定，當量濃度優(yōu)于摩爾濃度在于相同體積的等當量溶液具有相同的中和能力，因為兩者具有相同的當量數。Inatitration,wecompareequivalentweightsofacidandbase.Thenumberofequivalentsofacidisequaltotheproductofthevolumeoftheacidsolutionanditsnormality.Thenumberofequivalentsofbaseistheproductofthevolumeofthebasesolutionanditsnormality.Neutralizationhastakenplacewhenthenumberofequivalentsofacidisequaltothenumberofequivalentsofbase.滴定時我們會比較酸與堿的當量。酸的當量數等于酸的體積乘以它的當量濃度，堿的當量數等于堿的體積乘以當量濃度。當酸與堿的當量數相等時，中和反應發(fā)生。Caremustbeexercisedthroughoutthetitrationprocedure.Theburetteshouldbethoroughlycleanedwithsoapandwater,rinsedwithtapwater,andfinally,rinsedwithdistilledwater.Justbeforeuse,theburetteshouldberinsedwithtwo5-mlportionsofthesolutiontobeusedintheburette.Thisisdonebyholdingtheburetteinasemi-horizontalpositionandrollingthesolutionaroundtheentireinnersurface.Allowthefinalrinsingtodrainthroughthetip.滴定過程要十分小心，滴定管必須用肥皂和水完全洗凈，再依次用自來水和蒸餾水沖洗。使用前滴定管還要用5-mL的使用溶液清洗兩遍，其過程為：將滴定管半平放，轉動滴定管使管內溶液與內表面充分浸潤，然后從滴定管尖嘴放掉潤洗溶液。Procedure

步驟Filltheburettetoapointabovethetopmarkingandallowthesolutiontorunoutuntilthebottomofthemeniscusisjustatthetopmarkingoftheburette.Theburettetipmustbecompletelyfilledtodeliverthevolumemeasured.在滴定管內引入溶液到高于頂端刻度線以上，然后從尖嘴處放出溶液直至凹液面與頂端刻線齊平，滴定管尖嘴要完全充滿溶液以放出準確的體積。Inaddition,theburettemustbecleanedthoroughlyafterusebecausesodiumhydroxideandothertypesofsolutionswilleventuallyfrosttheglassandrenderanexpensivepieceofequipmentuseless.此外滴定管在使用后也要完全洗凈，因為氫氧化鈉和其它類型的試劑會腐蝕玻璃，導致滴定管的某個昂貴組件無法使用。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燒杯，加入兩滴酚酞指示劑，將1當量的氫氧化鈉濃度裝入堿式滴定管，并按上述操作放出多余的溶液。從滴定管將氫氧化鈉加入到燒杯與食醋反應，直至過量的一滴氫氧化鈉使酚酞產生淺粉色，滴定過程中要一直振蕩溶液。粉色的出現表明酸已完全被堿中和，過量的一滴氫氧化鈉與指示劑反應使其變色。讀出滴定管的刻度，記下中和食醋的氫氧化鈉的體積。Accordingtotheequation：NaOH+CH3COOH→Na++CH3COO-+H2OOnemoleculeofNaOHneutralizesonemoleculeofaceticacid,oronegram-molecularweightofNaOHneutralizesonegram-molecularweightofaceticacid.Calculatetheamountofaceticacidpresentinthevinegar.Reportthisamountasthepercentageofaceticacid.根據反應式NaOH+CH3COOH→Na++CH3COO-+H2O，一分子氫氧化鈉中和一分子的乙酸，或一克分子量的氫氧化鈉中和一克分子量的乙酸。然后計算出醋中乙酸的含量，用乙酸的百分比來表示。2.StandardTitrationCurveIfapHmeterisavailable,repeattheaboveprocessusingapHmeterforconstantlydeterminingthepH.Whentheendpointisreached,continueaddingthebasetoexpandthecurvefurther.Makeagraphforthistitration.

2.標準滴定曲線：如果有一個pH計，重復上述滴定過程，同時用pH計測定體系的pH值，到達滴定終點后，繼續(xù)滴加氫氧化鈉并記錄pH值，作一張（滴定劑消耗量vspH值的）滴定曲線圖。3.EquivalentsofAcidUsingthe1NsolutionofNaOH,determinethenumberofequivalentsintwosamplesofbenzoicacid.Carryouttheprocedureforthetwodeterminationssimultaneously.Fromthisvaluecalculatetheequivalentweightoftheacid.Thesolidshouldbeweighedinabeakerandshouldbedissolvedinabout25mlofethylalcoholbeforetitrationwiththebase.Between2.0and2.2gofthesolidprovidethebestresults.Recordalldataandmakeallcalculationsnecessarytodeterminetheequivalentweightofthesolidacid.Compareyourexperimentalvaluewiththeequivalentweightofbenzoicacid(calculatedfromtheformula)anddeterminethepercentageoferrorofyourwork.

3.酸的當量：用一當量濃度的氫氧化鈉，測定兩個苯甲酸樣品的當量數，