第二十四章容量

Lesson24.VolumetricAnalysis學(xué)習(xí)詞匯常用的化學(xué)實(shí)驗(yàn)儀器3.練習(xí)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(xué)計(jì)量的endpoint終點(diǎn)titration滴定molarity摩爾濃度normality當(dāng)量濃度equivalent當(dāng)量grammolecularweight克分子量moleweight分子量curve曲線(xiàn)graph曲線(xiàn)圖representation代表，象征marking刻度，條紋，標(biāo)志burette滴定管tapwater自來(lái)水rinse沖洗drain依次排出vinegar醋methylred甲基紅record記錄pHmeterpH計(jì)frost霜，霜化render致使，使成為simultaneously同時(shí)地inthecaseof在…情況下，要是bringabout導(dǎo)致，引起1.學(xué)習(xí)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?；?/p>

normalityn.當(dāng)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(xué)實(shí)驗(yàn)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?jī)煽跓?-neckBoilingflask集氣瓶gas-jarAlcohol

burnerwiregauzegas-jarroundbottomflaskStopperStopperRingstandwithring廣口瓶Widemouthbottle滴瓶Dropping

bottle

溫度計(jì)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(xí)全文翻譯Chemicalanalysescanbemadebydetermininghowmuchofasolutionofknownconcentrationisneededtoreactfullywithanunknowntestsample.Themethodisgenerallyreferredtoasvolumetricanalysisandconsistsoftitratingtheunknownsolutionwiththeoneofknownconcentration(astandardsolution).Bytitration,youcandetermineexactlyhowmuchofareagentisrequiredtobringaboutcompletereactionofthetestsolution.化學(xué)分析的一般通過(guò)測(cè)定一已知濃度的溶液與未知試樣完全反應(yīng)的關(guān)系來(lái)進(jìn)行，該方法一般也稱(chēng)為容量分析，方式是用已知濃度的標(biāo)準(zhǔn)溶液來(lái)滴定未知溶液。通過(guò)滴定分析，你可以測(cè)定與試樣完全反應(yīng)的標(biāo)準(zhǔn)溶液的消耗量。Generalprinciples

通用原理Usually,completionofthereactionisindicatedbyasudden,visiblechangeinthereactionsystemthatcoincideswiththestoichiometricrelationshipbetweenmolesorequivalentsof-thereagentsolutionandthereactantinthetestsolution.Adroportwoofanappropriateindicatorsolutionproducesacolorchangeatthepointwherethereactioniscomplete-referredtoastheendpoint.一般來(lái)說(shuō)，反應(yīng)體系出現(xiàn)可見(jiàn)的突變表明反應(yīng)已完全進(jìn)行，此時(shí)滴定劑與被滴定物質(zhì)的摩爾數(shù)或當(dāng)量滿(mǎn)足一定的化學(xué)計(jì)量關(guān)系。1~2滴合適的指示劑可在某個(gè)時(shí)刻產(chǎn)生顏色突變，此時(shí)滴定反應(yīng)完全進(jìn)行，稱(chēng)為滴定終點(diǎn)。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(zhì)的摩爾數(shù)（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(dāng)量濃度是一升溶液中某物質(zhì)的當(dāng)量數(shù)，酸的當(dāng)量指能提供1摩爾氫離子的酸的質(zhì)量，堿的當(dāng)量是接受1摩爾氫離子的堿的質(zhì)量。硫酸的當(dāng)量為98.08g除以2或49.04g，因此一當(dāng)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(dāng)量濃度可用滴定分析測(cè)定，當(dāng)量濃度優(yōu)于摩爾濃度在于相同體積的等當(dāng)量溶液具有相同的中和能力，因?yàn)閮烧呔哂邢嗤漠?dāng)量數(shù)。Inatitration,wecompareequivalentweightsofacidandbase.Thenumberofequivalentsofacidisequaltotheproductofthevolumeoftheacidsolutionanditsnormality.Thenumberofequivalentsofbaseistheproductofthevolumeofthebasesolutionanditsnormality.Neutralizationhastakenplacewhenthenumberofequivalentsofacidisequaltothenumberofequivalentsofbase.滴定時(shí)我們會(huì)比較酸與堿的當(dāng)量。酸的當(dāng)量數(shù)等于酸的體積乘以它的當(dāng)量濃度，堿的當(dāng)量數(shù)等于堿的體積乘以當(dāng)量濃度。當(dāng)酸與堿的當(dāng)量數(shù)相等時(shí)，中和反應(yīng)發(fā)生。Caremustbeexercisedthroughoutthetitrationprocedure.Theburetteshouldbethoroughlycleanedwithsoapandwater,rinsedwithtapwater,andfinally,rinsedwithdistilledwater.Justbeforeuse,theburetteshouldberinsedwithtwo5-mlportionsofthesolutiontobeusedintheburette.Thisisdonebyholdingtheburetteinasemi-horizontalpositionandrollingthesolutionaroundtheentireinnersurface.Allowthefinalrinsingtodrainthroughthetip.滴定過(guò)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(lái)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(guò)程為：將滴定管半平放，轉(zhuǎn)動(dòng)滴定管使管內(nèi)溶液與內(nèi)表面充分浸潤(rùn)，然后從滴定管尖嘴放掉潤(rùn)洗溶液。Procedure

步驟Filltheburettetoapointabovethetopmarkingandallowthesolutiontorunoutuntilthebottomofthemeniscusisjustatthetopmarkingoftheburette.Theburettetipmustbecompletelyfilledtodeliverthevolumemeasured.在滴定管內(nèi)引入溶液到高于頂端刻度線(xiàn)以上，然后從尖嘴處放出溶液直至凹液面與頂端刻線(xiàn)齊平，滴定管尖嘴要完全充滿(mǎn)溶液以放出準(zhǔn)確的體積。Inaddition,theburettemustbecleanedthoroughlyafterusebecausesodiumhydroxideandothertypesofsolutionswilleventuallyfrosttheglassandrenderanexpensivepieceofequipmentuseless.此外滴定管在使用后也要完全洗凈，因?yàn)闅溲趸c和其它類(lèi)型的試劑會(huì)腐蝕玻璃，導(dǎo)致滴定管的某個(gè)昂貴組件無(wú)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(dāng)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(yīng)，直至過(guò)量的一滴氫氧化鈉使酚酞產(chǎn)生淺粉色，滴定過(guò)程中要一直振蕩溶液。粉色的出現(xiàn)表明酸已完全被堿中和，過(guò)量的一滴氫氧化鈉與指示劑反應(yīng)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(jù)反應(yīng)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(jì)算出醋中乙酸的含量，用乙酸的百分比來(lái)表示。2.StandardTitrationCurveIfapHmeterisavailable,repeattheaboveprocessusingapHmeterforconstantlydeterminingthepH.Whentheendpointisreached,continueaddingthebasetoexpandthecurvefurther.Makeagraphforthistitration.

2.標(biāo)準(zhǔn)滴定曲線(xiàn)：如果有一個(gè)pH計(jì)，重復(fù)上述滴定過(guò)程，同時(shí)用pH計(jì)測(cè)定體系的pH值，到達(dá)滴定終點(diǎn)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(xiàn)圖。3.EquivalentsofAcidUsingthe1NsolutionofNaOH,determinethenumberofequivalentsintwosamplesofbenzoicacid.Carryouttheprocedureforthetwodeterminationssimultaneously.Fromthisvaluecalculatetheequivalentweightoftheacid.Thesolidshouldbeweighedinabeakerandshouldbedissolvedinabout25mlofethylalcoholbeforetitrationwiththebase.Between2.0and2.2gofthesolidprovidethebestresults.Recordalldataandmakeallcalculationsnecessarytodeterminetheequivalentweightofthesolidacid.Compareyourexperimentalvaluewiththeequivalentweightofbenzoicacid(calculatedfromtheformula)anddeterminethepercentageoferrorofyourwork.

3.酸的當(dāng)量：用一當(dāng)量濃度的氫氧化鈉，測(cè)定兩個(gè)苯甲酸樣品的當(dāng)量數(shù)，