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Acid-BaseEquilibriaChapter17Copyright
©TheMcGraw-HillCompanies,Inc.
Permissionrequiredforreproductionordisplay.Acid-BaseEquilibriaChapter171Chapter17:Acid-BaseEquilibriaBufferCompositionpHofBufferSolutionspHaftersmallamountsofacid/baseaddedDesigningBufferSolutionsAcid-BaseTitrationsIndicatorChapter17:Acid-BaseEquilibr2Abuffersolutionisasolutionof:AweakacidanditsconjugatebaseorAweakbaseanditconjugateacidAbuffersolutionhastheabilitytoresistlargechangesinpHupontheadditionofsmallamountsofeitheracidorbase.16.3Note:Ifeithertheacidorbaseisanegative orpositiveion;itwillbefoundinthe formofasalt.Note:Itisimportantthattheacidandbase havetheconjugate relationship.Abuffersolutionisasolutio3SixStrongAcids
HClH2SO4HBrHClO4HIHNO3SixStrongAcids
HClH2SO4HBrHC4Whichofthefollowingarebuffersystems?(a)KF/HF(b)KBr/HBr,(c)Na2CO3/NaHCO3F-isaweakbaseandHFisitsweakconjugateacidbuffersolution(b)HBrisastrongacidnotabuffersolution(c)CO32-isaweakbaseandHCO3-isitconjugateacidbuffersolution16.3Whichofthefollowingarebuf5HowaBufferWithstandsLargeChangesinpH
(CH3COO)H/Na(CH3COO-)HowaBufferWithstandsLarge6ConsideranequalmolarmixtureofCH3COOHandCH3COONaAddstrongacidH+
(aq)+CH3COO-
(aq)CH3COOH(aq)AddstrongbaseOH-
(aq)+CH3COOH(aq)CH3COO-
(aq)+H2O(l)HowaBufferWithstandsLargeChangesinpH
(CH3COO)H/Na(CH3COO-)BaseofbufferremovesexcessH+AcidofbufferremovesexcessOH-Consideranequalmolarmixtur7HowaBufferWithstandsLargeChangesinpH
(CH3COO)H/Na(CH3COO-)IntroductoryChemistry2/ebyNTro,PrenticeHall,2019,pg495HowaBufferWithstandsLarge8Abuffersolutionisthemosteffectiveif... 1)therearelargeamountsofacid/conjugatebase 2)theamountsofacidandconjugatebaseare aboutequalTofindpHofbuffermadeof;HF/F- HF(aq)<->H+(aq)+F-(aq)Ka=[H+][F-][HF]H+=Ka[HF][F-]Iftheratio([HA]/[A-])staysaboutsame;pHwillnotchangedramatically!Abuffersolutionisthemost9Abuffersolutionisthemosteffectiveif...
1)therearelargeamountsofacid/conjugatebase
2)theamountsofacidandconjugatebaseareaboutequalHFF-AddH+HFF-AddOH-HFF-H+(aq)+F-(aq)<->HF(aq)FreeH+reactswith/removesbase(F-)ofbufferandproducesmoreHF.OH-(aq)+HF(aq)<-> F-(aq)+H2O(l)Free(OH)-reactswith/removesacid(HF)ofbufferandproducesmoreF-.Abuffersolutionisthemost10Abuffersolutionisthemosteffectiveif...
1)therearelargeamountsofacid/conjugatebase
2)theamountsofacidandconjugatebaseareaboutequalHFF-AddH+HFF-AddOH-HFF-5000=150005002=1.000849984998=0.99950025=157=2.33333=0.42867Abuffersolutionisthemost11DeterminingthepH
ofBufferSolutionsThecalculationsareverysimilartodeterminingthepHofweakacidsolutions–theonlydifferenceisthatinitiallytherearebothsomereactantsandproductspresent.DeterminingthepH
ofBuffer12Aneasierwaytodetermine
pHofBuffersolutionsHenderson-HasselbalchequationAneasierwaytodetermine
pH13ConsidermixtureofsaltNaAandweakacidHA.HA(aq)H+
(aq)+A-
(aq)Ka=[H+][A-][HA][H+]=Ka[HA][A-]-log[H+]=-logKa
[HA][A-]pH=pKa+log[A-][HA]Henderson-Hasselbalchequation-log[H+]=-logKa-log[HA][A-][conjugatebase]pH=pKa+log[weakacid]pH=pKa+log[A-][HA]InsignificantChangeApproximationisAssumedInThisEquation!ConsidermixtureofsaltNaAa14WhatisthepHofasolutioncontaining0.30MHCOOHand0.52MHCOOK?HCOOH(aq)H+
(aq)+HCOO-
(aq)Initial(M)Change(M)Equilibrium(M)0.300.00-x+x0.30-x0.52+xx0.52+xCommonioneffect0.30–x
0.300.52+x
0.52pH=pKa+log[HCOO-][HCOOH]HCOOHpKa=3.77pH=3.77+log[0.52][0.30]=4.0116.2Mixtureofweakacidandconjugatebase!WhatisthepHofasolutionc15=9.20CalculatethepHofthe0.30MNH3/0.36MNH4Clbuffersystem.WhatisthepHaftertheadditionof20.0mLof0.050MNaOHto80.0mLofthebuffersolution?NH4+
(aq)H+
(aq)+NH3
(aq)pH=pKa+log[NH3][NH4+]pKa
=9.25pH=9.25+log[0.30][0.36]=9.17NH4+
(aq)+OH-
(aq)H2O(l)+NH3
(aq)start(moles)end(moles)0.0290.0010.0240.0280.00.025pH=9.25+log[0.25][0.28][NH4+]=0.0280.10finalvolume=80.0mL+20.0mL=100mL[NH3]=0.0250.1016.3=9.20CalculatethepHofthe16DesigningBufferSolutionspH=pKa+log{[X-]/[HX]}Buffersaremosteffectiveifthereareequalandlargeamountsofweakacidandconjugatebase. [X-]=[HX]pH=pKa+log(1)pH=pKaDesigningBufferSolutionspH=17pKaofWeakAcidsWeakAcidpKaHydrofluoricAcid3.15BenzoicAcid4.19CarbonicAcid6.38HydrocyanicAcid9.31pKaofWeakAcidsWeakAcidpKaH18TitrationsInatitrationasolutionofaccuratelyknownconcentrationisaddedgraduallyaddedtoanothersolutionofunknownconcentrationuntilthechemicalreactionbetweenthetwosolutionsiscomplete.Equivalencepoint–thepointatwhichthereactioniscompleteIndicator–substancethatchangescolorat(ornear)theequivalencepointSlowlyaddbasetounknownacidUNTILTheindicatorchangescolor(pink)4.7TitrationsInatitrationasol19Acid-BaseTitrationsIntroductoryChemistry2/ebyNTro,PrenticeHall,2019,pg480Acid-BaseTitrationsIntroducto20Atendpoint/equivalencepoint
molesH+=moles(OH)-
MV(acid)=MV(base)Twowaystogetendpoint/equivalencepointColorchangeMid-pointofsteepriseofacid/basetitrationcurveAtendpoint/equivalencepoint21StrongAcid-StrongBaseTitrationsNaOH(aq)+HCl(aq)H2O(l)+NaCl(aq)0.10MNaOHaddedto25mLof0.10MHCl16.4neutralsaltStrongAcid-StrongBaseTitrat22WeakAcid-StrongBaseTitrationsCH3COOH(aq)+NaOH(aq)CH3COONa(aq)+H2O(l)Atequivalencepoint(pH>7):16.4BasicSaltWeakAcid-StrongBaseTitratio23StrongAcid-WeakBaseTitrationsHCl(aq)+NH3
(aq)NH4Cl(aq)Atequivalencepoint(pH<7):16.4AcidicSaltStrongAcid-WeakBaseTitratio24Acid-Base-Equilibria-and-Solubility-Equilibria酸碱平衡与溶解度平衡课件25Thetitrationcurveofastrongacidwithastrongbase.16.5Thetitrationcurveofastron26Whichindicator(s)wouldyouuseforatitrationofHNO2withKOH?Weakacidtitratedwithstrongbase.Atequivalencepoint,willhaveconjugatebaseofweakacid.Atequivalencepoint,pH>7Usecresolredorphenolphthalein16.5Whichindicator(s)wouldyouu27谢谢！谢谢！28Acid-BaseEquilibriaChapter17Copyright
©TheMcGraw-HillCompanies,Inc.
Permissionrequiredforreproductionordisplay.Acid-BaseEquilibriaChapter1729Chapter17:Acid-BaseEquilibriaBufferCompositionpHofBufferSolutionspHaftersmallamountsofacid/baseaddedDesigningBufferSolutionsAcid-BaseTitrationsIndicatorChapter17:Acid-BaseEquilibr30Abuffersolutionisasolutionof:AweakacidanditsconjugatebaseorAweakbaseanditconjugateacidAbuffersolutionhastheabilitytoresistlargechangesinpHupontheadditionofsmallamountsofeitheracidorbase.16.3Note:Ifeithertheacidorbaseisanegative orpositiveion;itwillbefoundinthe formofasalt.Note:Itisimportantthattheacidandbase havetheconjugate relationship.Abuffersolutionisasolutio31SixStrongAcids
HClH2SO4HBrHClO4HIHNO3SixStrongAcids
HClH2SO4HBrHC32Whichofthefollowingarebuffersystems?(a)KF/HF(b)KBr/HBr,(c)Na2CO3/NaHCO3F-isaweakbaseandHFisitsweakconjugateacidbuffersolution(b)HBrisastrongacidnotabuffersolution(c)CO32-isaweakbaseandHCO3-isitconjugateacidbuffersolution16.3Whichofthefollowingarebuf33HowaBufferWithstandsLargeChangesinpH
(CH3COO)H/Na(CH3COO-)HowaBufferWithstandsLarge34ConsideranequalmolarmixtureofCH3COOHandCH3COONaAddstrongacidH+
(aq)+CH3COO-
(aq)CH3COOH(aq)AddstrongbaseOH-
(aq)+CH3COOH(aq)CH3COO-
(aq)+H2O(l)HowaBufferWithstandsLargeChangesinpH
(CH3COO)H/Na(CH3COO-)BaseofbufferremovesexcessH+AcidofbufferremovesexcessOH-Consideranequalmolarmixtur35HowaBufferWithstandsLargeChangesinpH
(CH3COO)H/Na(CH3COO-)IntroductoryChemistry2/ebyNTro,PrenticeHall,2019,pg495HowaBufferWithstandsLarge36Abuffersolutionisthemosteffectiveif... 1)therearelargeamountsofacid/conjugatebase 2)theamountsofacidandconjugatebaseare aboutequalTofindpHofbuffermadeof;HF/F- HF(aq)<->H+(aq)+F-(aq)Ka=[H+][F-][HF]H+=Ka[HF][F-]Iftheratio([HA]/[A-])staysaboutsame;pHwillnotchangedramatically!Abuffersolutionisthemost37Abuffersolutionisthemosteffectiveif...
1)therearelargeamountsofacid/conjugatebase
2)theamountsofacidandconjugatebaseareaboutequalHFF-AddH+HFF-AddOH-HFF-H+(aq)+F-(aq)<->HF(aq)FreeH+reactswith/removesbase(F-)ofbufferandproducesmoreHF.OH-(aq)+HF(aq)<-> F-(aq)+H2O(l)Free(OH)-reactswith/removesacid(HF)ofbufferandproducesmoreF-.Abuffersolutionisthemost38Abuffersolutionisthemosteffectiveif...
1)therearelargeamountsofacid/conjugatebase
2)theamountsofacidandconjugatebaseareaboutequalHFF-AddH+HFF-AddOH-HFF-5000=150005002=1.000849984998=0.99950025=157=2.33333=0.42867Abuffersolutionisthemost39DeterminingthepH
ofBufferSolutionsThecalculationsareverysimilartodeterminingthepHofweakacidsolutions–theonlydifferenceisthatinitiallytherearebothsomereactantsandproductspresent.DeterminingthepH
ofBuffer40Aneasierwaytodetermine
pHofBuffersolutionsHenderson-HasselbalchequationAneasierwaytodetermine
pH41ConsidermixtureofsaltNaAandweakacidHA.HA(aq)H+
(aq)+A-
(aq)Ka=[H+][A-][HA][H+]=Ka[HA][A-]-log[H+]=-logKa
[HA][A-]pH=pKa+log[A-][HA]Henderson-Hasselbalchequation-log[H+]=-logKa-log[HA][A-][conjugatebase]pH=pKa+log[weakacid]pH=pKa+log[A-][HA]InsignificantChangeApproximationisAssumedInThisEquation!ConsidermixtureofsaltNaAa42WhatisthepHofasolutioncontaining0.30MHCOOHand0.52MHCOOK?HCOOH(aq)H+
(aq)+HCOO-
(aq)Initial(M)Change(M)Equilibrium(M)0.300.00-x+x0.30-x0.52+xx0.52+xCommonioneffect0.30–x
0.300.52+x
0.52pH=pKa+log[HCOO-][HCOOH]HCOOHpKa=3.77pH=3.77+log[0.52][0.30]=4.0116.2Mixtureofweakacidandconjugatebase!WhatisthepHofasolutionc43=9.20CalculatethepHofthe0.30MNH3/0.36MNH4Clbuffersystem.WhatisthepHaftertheadditionof20.0mLof0.050MNaOHto80.0mLofthebuffersolution?NH4+
(aq)H+
(aq)+NH3
(aq)pH=pKa+log[NH3][NH4+]pKa
=9.25pH=9.25+log[0.30][0.36]=9.17NH4+
(aq)+OH-
(aq)H2O(l)+NH3
(aq)start(moles)end(moles)0.0290.0010.0240.0280.00.025pH=9.25+log[0.25][0.28][NH4+]=0.0280.10finalvolume=80.0mL+20.0mL=100mL[NH3]=0.0250.1016.3=9.20CalculatethepHofthe44DesigningBufferSolutionspH=pKa+log{[X-]/[HX]}Buffersaremosteffectiveifthereareequalandlargeamountsofweakacidandconjugatebase. [X-]=[HX]pH=pKa+log(1)pH=pKaDesigningBufferSolutionspH=45pKaofWeakAcidsWeakAcidpKaHydrofluoricAcid3.15BenzoicAcid4.19CarbonicAcid6.38HydrocyanicAcid9.31pKaofWeakAcidsWeakAcidpKaH46TitrationsInatitrationasolutionofaccuratelyknownconcentrationisaddedgraduallyaddedtoanothersolutionofunknownconcentrationuntilthechemicalreactionbetweenthetwosolutionsiscomplete.Equivalencepoint–thepointatwhichthereactioniscompleteIndicator–substancethatchangescolorat(ornear)theequivalencepointSlowly
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