酸碱滴定实验.doc

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1、ACIDBASETITRATIONCHEMISTRYLABINTRODUCTION:Inthechemistrylaboratory,itissometimesnecessarytoexperimentallydeterminetheconcentrationofanunknownacidorbasesolution.Aprocedureformakingthiskindofdeterminationiscalledanacid-basetitration.Inthisprocedure,asolutionofknownconcentration,calledthestandardsolu

2、tion,isusedtoneutralizeapreciselymeasurevolumeofthesolutionofunknownconcentration,towhichoneortwodropsofanappropriateacids-baseindicatorhavebeenadded.Ifthesolutionofunknownconcentrationisacidic,astandardbasesolutionisaddedtotheacidsolutionuntilitisneutralized.Ifthesolutionofunknownconcentrationisb

3、asic,astandardacidsolutionisaddedtothebasesolutionuntilitisneutralized.Whilecarryingoutanacid-basetitration,youmustbeabletorecognizewhentostopaddingthestandardsolution,thatis,whenneutralizationisreached.Thisisthepurposeoftheacid-baseindicatormentionedabove.Asuddenchangeincoloroftheindicatorsignals

4、thatneutralizationhasoccurred.Atthispoint,thenumberofhydroniumionsfromtheacidequalsthenumberofhydroxideionsfromthebase.Thepointatwhichthisoccursiscalledtheendpointofthetitration.Whentheendpointisreached,thevolumeofthestandardsolutioniscarefullydetermined.Then,themeasuredvolumesofthetwosolutionsand

5、theknownconcentrationofthestandardsolutioncanbeusedtocalculatetheconcentrationoftheunknownsolution.Thefollowingstepstellushowtocalculatetheunknownconcentration:1.Writethebalancedequationforthereaction:Acid+BaseàSalt+HOHFromthecoefficients,determinehowmanymolesofacidreactwithmolesofbase2.Thefollowi

6、ngrelationshipcanbeusedtocalculatetheunknownconcentration(note:thecoefficientsofacid&basecomefromthebalancedequation)(H+)xMAxVA=(OH-)xMBxVBWhereMA=molarityofacidsolutionMB=molarityofbasesolutionVA=volumeofacidsolutionVB=volumeofbasesolutionH+=molesofhydroniumionsintheacidOH-=molesofhydroxideionsin

7、thebaseExample#1:Step1:H2SO4+2NaOHàNa2SO4+2HOHStep2:(2)xMAxVA=(1)xMBxVBPURPOSE:TodeterminethemolarityofaNaOHsolutionbytitratingitwithastandardacidsolutionEQUIPMENT:50mLburet2Erlenmeyerflasks,150mLfunnelRingstandd