医用基础化学英文版PPT课件PPT课件下载推荐.ppt
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医用基础化学英文版PPT课件PPT课件下载推荐.ppt
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TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityChapter4BufferSolutionTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversitysolutionsthatresistchangeinhydroniumion,H+,andthehydroxideion,OH-,concentration(andconsequentlypH)uponadditionofsmallamountsofacidorbase,orupondilution.4.1.1TheEssentialFeatureofaBufferBufferSolution:
@#@4.1CompositionandActionofBufferSolutionsTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityBuffersaremixturescontainingacommonion:
@#@eitherweakacidsandtheirconjugatebasesorweakbasesandtheirconjugateacid.Twocommonbuffers:
@#@ammonium-ammonia,carbonate-bicarbonateNH4+(aq)H+(aq)+NH3(aq)CO3-2(aq)+H2O(l)HCO3-1(aq)+OH-1(aq)TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityBuffersystemConjugateacidConjugatebasepKa(at25)HAcNaAcHAcAc-4.76H2CO3NaHCO3H2CO3HCO3-6.35H3PO4NaH2PO4H3PO4H2PO4-2.16TrisHClTrisTrisH+Tris7.85H2C8H4O4KHC8H4O4H2C8H4O4HC8H4O4-2.89NH4ClNH3NH4+NH39.25CH3NH3+Cl-CH3NH2CH3NH3+CH3NH210.63NaH2PO4Na2HPO4H2PO4-HPO42-7.21BuffersystemsthatareusefulatvariouspHvaluesTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityTris:
@#@Tris(Hydroxymethy)methanamin三羟甲基氨基甲烷三羟甲基氨基甲烷CCH2OHCH2OHHOH2CNH2TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityABufferedSolutionresistschangeinitspHwheneitherH+orOHareadded.1.0Lof0.50MCH3COOH+0.50MCH3COONapH=4.74Adding0.010molsolidNaOHraisesthepHofthesolutionto4.76,averyminorchange.TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityTheeffectofadditionofacidorbasetoanunbufferedsolutionabufferedsolutionacidaddedbaseaddedacidaddedbaseaddedTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityBufferwithequalconcentrationsofconjugatebaseandacidOH-H3O+BufferafteradditionofH3O+H2O+CH3COOHH3O+CH3COO-BufferafteradditionofOH-CH3COOH+OH-H2O+CH3COO-4.1.2HowaBufferWorksTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityHAc+H2OH3O+AcH+Shiftleft+OHH2OShiftrightAnti-acidAnti-baseanti-acidmechanismanti-basemechanismTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityTheamountsofweakacidandweakbaseinthebuffermustbesignificantlylargerthantheamountsofH3O+orOH-thatwillbeadded,otherwisethepHcannotremainapproximatelyconstant.Thusadditionoflimitedamountsofastrongacidorbaseiscounteractedbythespeciespresentinthebuffersolution,andthepHchangesverylittle.NosolutioncankeepthepHapproximatelyconstantifyouaddlargeramountsofeitheracidorbasethatarepresentintheoriginalbuffer.TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityForaHB-NaBbuffersystem,HB+H2OH3O+BNaBNa+BKa=H+BHBH+=KaHBBApplylogonbothsidesofaboveequation,pH=pKa+lgBHBTheHenderson-HasselbalchEquation4.2TheHenderson-HasselbalchEquationThepHofbuffersolutionTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversitypH=pKa+lgBHB=pKa+lgconjugatebaseconjugateacidpKa:
@#@thelogofKaoftheconjugateacidB、HB:
@#@equilibriumconcentrationB/HB:
@#@bufferratioB+HB:
@#@totalconcentrationHB=cHBcHB(dissociated)B=cNaB+cHB(dissociated)cHBcNaBTheHenderson-HasselbalchEquationTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversitypH=pKa+lgcBcHB=pKa+lgnB/VnHB/VpH=pKa+lgnBnHBIftheconcentrationsofconjugateacidandbaseusedareequal,i.e.cB=cHB.pH=pKa+lgcBVBcHBVHB=pKa+lgVBVHBthreedifferenttypesofofHenderson-HasselbalchEquationFightdilutionTheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityCalculatingthepHofaBufferSolution-1PROBLEMSampleProblem4-1Abufferispreparedbymixingequalvolumesof0.1molL-1NaAcand0.2molL-1HAc.WhatisthepHofthefinalsolution?
@#@ThepKaofHAcis4.74.WhatwillthepHbeaftertheadditionof0.005molofNaOH(s)to500mLofthebuffersolutiondescribedabove?
@#@TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversitySOLUTIONBeforetheadditionof0.005molofNaOH(s)to500mLofthebuffersolutionCalculatingthepHofaBufferSolution-1SampleProblem4-1TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversitySOLUTIONAftertheadditionof0.005molofNaOH(s)to500mLofthebuffersolutionCalculatingthepHofaBufferSolution-1SampleProblem4-1TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversityCalculatingthepHofaBufferSolution-2PROBLEMSampleProblem4-2CalculatethepHofabufferpreparedbymixingHAwithNaA.ThebuffercontainsHAataconcentrationof0.25molL-1.After0.20gNaOHisaddedto100mLofthisbuffer,thepHoftheresultingsolutionis5.60.Theacid-ionizationconstantofHAis5.010-6(pKa=5.3).TheCollegeofChemistryandChemicalEngineeringCentralSouthUniversitySOLUTIONHA(aq)+OH-(aq)A-(aq)+H2O(
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