Supplement_2_The_Properties_of_Buffers.pdf

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1、Supplement2ThePropertiesofBuffersBACKGROUDForaweekacidsolution:+θHAH++A-[]HK=ac,11+θpHHp=−lg[]=Kc−lga22Forabuffersolution,suchasCH3COOH/CH3COONa:−[]CHCOO[]ConjugateBase3pH=+pKlog=+pKlogaa[]CHCOOH[]WeakAcid3PROCEDURE--PartA.StrongandWeakAcids1.Prepare50mL0.50MCH3COOHsolution:Pipet5.00mLof5.0M

2、CH3COOHsolutionintoa50mlvolumetricflask.Dilutethesolutionbyfillingthevolumetricflaskwithde-ionizedwateruntilthemeniscusreachthemark.2.UsethepHmetertorecordthepHofthe0.50MHClsolution,the0.50MCH3COOHsolutionandoneoftheunknowHAcsolutions.3.PlaceashortlengthofMgstripinthebottomoftheemptywells,ad

3、dthesameamountof0.50MHClsolutionandHAcsolutiontojustcovertheMg,recordyourobservations.PROCEDURE---PartB.DesigningaBuffer(makebufferswith5.0MCH3COOHand2.0MCH3COONasolutions)¢Buffer1—0.100LofapH=4.15bufferwithatotalconcentrationof0.100M¢Buffer2—0.100LofapH=4.75bufferwithatotalconcentrationof0.

4、100M¢Buffer3—0.100LofapH=4.57bufferwithatotalconcentrationof0.100M¢Buffer4—0.100LofapH=5.35bufferwithatotalconcentrationof0.100M¢Buffer5—0.100LofapH=4.93bufferwithatotalconcentrationof0.100M1.Prepare0.100Lofthebufferina100-mLvolumetricflask:PipetxmLof5.0MCH3COOHandymLof2.00MCH3COONasolutioni

5、ntoa100mLvolumetricflask.Dilutethesolutionbyfillingthevolumetricflaskwithde-ionizedwateruntilthemeniscusreachthemark.BufferpHcb/cax(5.00MCH3COOH)(mL)y(2.00MCH3COONa)(mL)14.1524.7534.5745.3554.932.WithapHmeter,recordtheinitialpHofeachbuffersolution.PROCEDURE---PartC.PropertiesofaBuffer1.Using

6、aclean50mLgraduatedcylinder,measurethird20.0mLportionsofyourbuffersolutionandpourintothreeseparate50-mLbeakers.Intwoother50-mLbeakers,measureouttwo20.0-mLportionsofH2O.2.WithapHmeter,recordtheinitialpHofeachbuffersolutionandH2O.Add5dropsof0.50MHCl/0.50MNaOH,oradd5mLH2Otoaseparatedbuffersolut

7、ion,swirlthesolutionandrecordthepH.RepeatthisprocedurewiththetwosamplesofH2O.PROCEDURE---PartD.DeterminationofBufferCapacity1.Filla20mLgraduatedcylinderwith0.50MNaOHsolution.RecordtheinitialvolumeV1.Addthe0.50MNaOHsolutiondrop-wiseintothebufferwith