Acids-and-Bases-Judson教学讲解课件

TheChemistryofAcidsandBasesChemistryIMr.TrottsJudsonSrHighSchoolAcidsandBasesQuizIndicatewhethereachcompoundisanacid,base,NeutralSalt(NS),dilute(D)orconcentrated(C)8MNi(OH)22MHBr12MNaOH.012MHC2H3O210MNaNO3AcidandBasesAcidandBasesAcidandBasesAcidsHaveasourtaste.Vinegarisasolutionofaceticacid.Citrusfruitscontaincitricacid.Reactwithcertainmetalstoproducehydrogengas.ReactwithcarbonatesandbicarbonatestoproducecarbondioxidegasHaveabittertaste.Feelslippery.Manysoapscontainbases.BasesSomePropertiesofAcidsProduceH+(asH3O+)ionsinwater(thehydroniumionisahydrogenionattachedtoawatermolecule)Tastesour CorrodemetalsElectrolytes Reactwithbasestoformasaltandwater pHislessthan7Turnsbluelitmuspapertored“BluetoRedA-CID”AcidNomenclatureReviewBinaryTernaryAneasywaytorememberwhichgoeswithwhich…“Inthecafeteria,you

ATE

something

ICky”AcidNomenclatureFlowchartHBr(aq)H2CO3H2SO3

hydrobromic

acid carbonic

acid sulfurous

acidAcidNomenclatureReview2-Bturnedin:Name‘Em!1.HI(aq)2.HCl(aq)3.H2SO3(sulfite)

4.HNO3(nitrate)5.HIO4(iodate)SomePropertiesofBasesProduceOH-ionsinwaterTastebitter,chalkyAreelectrolytesFeelsoapy,slipperyReactwithacidstoformsaltsandwaterpHgreaterthan7Turnsredlitmuspapertoblue“BasicBlue”SomeCommonBases

NaOH sodiumhydroxide lye KOH potassiumhydroxide liquidsoap Ba(OH)2 bariumhydroxide stabilizerforplastics Mg(OH)2 magnesiumhydroxide “MOM”MilkofmagnesiaAl(OH)3 aluminumhydroxide Maalox(antacid)Acid/BasedefinitionsDefinition#1:Arrhenius(traditional)Acids–produceH+ions(orhydroniumionsH3O+)Bases–produceOH-ions(problem:somebasesdon’thavehydroxideions!)ArrheniusacidisasubstancethatproducesH+(H3O+)inwaterArrheniusbaseisasubstancethatproducesOH-inwaterAcid/BaseDefinitionsDefinition#2:Brønsted–LowryAcids–protondonorBases–protonacceptorA“proton”isreallyjustahydrogenatomthathaslostit’selectron!ABrønsted-Lowry

acid

isaprotondonorABrønsted-Lowry

base

isaprotonacceptoracidconjugate

basebaseconjugate

acidACID-BASETHEORIESTheBrønsteddefinitionmeansNH3isa

BASE

inwater—andwaterisitselfan

ACIDConjugatePairs2Bturnedin:LearningCheck!Labeltheacid,base,conjugateacid,andconjugatebaseineachreaction:HONORSONLY!6.HCl+OH-

Cl-+H2O

7.H2O+H2SO4

HSO4-+H3O+

Acids&BaseDefinitionsLewisacid-asubstancethatacceptsanelectronpairLewisbase-asubstancethatdonatesanelectronpairDefinition#3–Lewis

Formationof

hydroniumionisalsoanexcellentexample.LewisAcids&BasesElectronpairofthenewO-HbondoriginatesontheLewisbase.LewisAcid/BaseReactionLewisAcid-BaseInteractionsinBiologyThehemegroupinhemoglobincaninteractwithO2andCO.TheFeioninhemoglobinisaLewisacidO2andCOcanactasLewisbasesHemegroupThepHscaleisawayofexpressingthestrengthofacidsandbases.Insteadofusingverysmallnumbers,wejustusetheNEGATIVEpowerof10ontheMolarityoftheH+(orOH-)ion.

Under7=acid

7=neutral

Over7=basepHofCommonSubstancesCalculatingthepHpH=-log[H+](Rememberthatthe[]meanMolarity)

Example:If[H+]=1X10-10

pH=-log1X10-10 pH=-(-10) pH=10Example:If[H+]=1.8X10-5

pH=-log1.8X10-5 pH=-(-4.74) pH=4.74TryThese!FindthepHofthese:1)A0.15MsolutionofHydrochloricacid2)A3.00X10-7MsolutionofNitricacidpHcalculations–SolvingforH+IfthepHofCokeis3.12,[H+]=???BecausepH=-log[H+]then -pH=log[H+]Takeantilog(10x)ofboth

sidesandget10-pH=

[H+][H+]=10-3.12=7.6x10-4M

***tofindantilogonyourcalculator,lookfor“Shift”or“2ndfunction”andthenthelogbuttonpHcalculations–SolvingforH+AsolutionhasapHof8.5.WhatistheMolarityofhydrogenionsinthesolution?pH=-log[H+]8.5=-log[H+]-8.5=log[H+]Antilog-8.5=antilog(log[H+])10-8.5=[H+]3.16X10-9=[H+]MoreAboutWaterH2OcanfunctionasbothanACIDandaBASE.Inpurewatertherecanbe

AUTOIONIZATIONEquilibriumconstantforwater=KwKw=[H3O+][OH-]=

1.00x10-14

at25oCHONORSONLY!MoreAboutWaterKw=[H3O+][OH-]=1.00x10-14at25oCInaneutralsolution[H3O+]=[OH-]soKw=[H3O+]2=[OH-]2andso[H3O+]=[OH-]=1.00x10-7MAutoionizationHONORSONLY!pOHSinceacidsandbasesareopposites,pHandpOHareopposites!pOHdoesnotreallyexist,butitisusefulforchangingbasestopH.pOHlooksattheperspectiveofabase

pOH=-log[OH-]SincepHandpOHareonoppositeends,

pH+pOH=14pH[H+][OH-]pOH[H3O+],[OH-]andpHWhatisthepHofthe 0.0010MNaOHsolution?[OH-]=0.0010(or1.0X10-3M)pOH=-log0.0010pOH=3 pH=14–3=11

ORKw=[H3O+][OH-][H3O+]=1.0x10-11MpH=-log(1.0x10-11)=11.00

ThepHofrainwatercollectedinacertainregionofthenortheasternUnitedStatesonaparticulardaywas4.82.WhatistheH+ionconcentrationoftherainwater?TheOH-ionconcentrationofabloodsampleis

2.5x10-7M.WhatisthepHoftheblood?[OH-][H+]pOHpH10-pOH10-pH-Log[H+]-Log[OH-]14-pOH14-pH1.0x10-14[OH-]1.0x10-14[H+]Calculating[H3O+],pH,[OH-],andpOHProblem1:Achemistdilutesconcentratedhydrochloricacidtomaketwosolutions:(a)3.0Mand(b)0.0024M.Calculatethe[H3O+],pH,[OH-],andpOHofthetwosolutionsat25°C.Problem2:Whatisthe[H3O+],[OH-],andpOHofasolutionwithpH=3.67?Isthisanacid,base,orneutral?Problem3:Problem#2withpH=8.05?

HNO3,HCl,H2SO4andHClO4areamongtheonlyknownstrongacids.StrongandWeakAcids/BasesThestrengthofanacid(orbase)isdeterminedbytheamountofIONIZATION.HONORSONLY!StrongandWeakAcids/BasesGenerallydivideacidsandbasesintoSTRONGorWEAKones.STRONGACID:

HNO3(aq)+H2O(l)---> H3O+(aq)+NO3-(aq)HNO3isabout100%dissociatedinwater.HONORSONLY!Weakacidsaremuchlessthan100%ionizedinwater.Oneofthebestknownisaceticacid=CH3CO2HStrongandWeakAcids/BasesHONORSONLY!StrongBase:

100%dissociatedinwater.

NaOH(aq)--->Na+(aq)+OH-(aq)StrongandWeakAcids/BasesOthercommonstrongbasesincludeKOHand

Ca(OH)2.CaO(lime)+H2O-->

Ca(OH)2(slakedlime)CaOHONORSONLY!Weakbase:

lessthan100%ionizedinwaterOneofthebestknownweakbasesisammoniaNH3(aq)+H2O(l)

NH4+(aq)+OH-(aq)StrongandWeakAcids/BasesHONORSONLY!WeakBasesHONORSONLY!EquilibriaInvolving

WeakAcidsandBasesConsideraceticacid,HC2H3O2(HOAc)HC2H3O2+H2OH3O++C2H3O2

-Acid Conj.base(KisdesignatedKaforACID)Kgivestheratioofions(splitup)tomolecules(don’tsplitup)HONORSONLY!IonizationConstantsforAcids/BasesAcidsConjugateBasesIncreasestrengthIncreasestrengthHONORSONLY!EquilibriumConstants

forWeakAcidsWeakacidhasKa<1Leadstosmall[H3O+]andapHof2-7

HONORSONLY!EquilibriumConstants

forWeakBasesWeakbasehasKb<1Leadstosmall[OH-]andapHof12-7

HONORSONLY!RelationofKa,Kb,[H3O+]andpHHONORSONLY!EquilibriaInvolvingAWeakAcidYouhave1.00MHOAc.Calc.theequilibriumconcs.ofHOAc,H3O+,OAc-,andthepH.Step1.

Defineequilibriumconcs.inICEtable.

[HOAc] [H3O+] [OAc-]initial change equilib 1.00 0 0-x +x +x1.00-x

x xHONORSONLY!EquilibriaInvolvingAWeakAcidStep2.

WriteKaexpression

Youhave1.00MHOAc.Calc.theequilibriumconcs.ofHOAc,H3O+,OAc-,andthepH.Thisisaquadratic.Solveusingquadraticformula.oryoucanmakeanapproximationifxisverysmall!(Ruleofthumb:10-5orsmallerisok)HONORSONLY!EquilibriaInvolvingAWeakAcidStep3.

SolveKaexpression

Youhave1.00MHOAc.Calc.theequilibriumconcs.ofHOAc,H3O+,OAc-,andthepH.FirstassumexisverysmallbecauseKaissosmall.Nowwecanmoreeasilysolvethisapproximateexpression.HONORSONLY!EquilibriaInvolvingAWeakAcidStep3.

SolveKa

approximate

expression

Youhave1.00MHOAc.Calc.theequilibriumconcs.ofHOAc,H3O+,OAc-,andthepH.x=

[H3O+]=[OAc-]=4.2x10-3MpH=-log[H3O+]=-log(4.2x10-3)=

2.37HONORSONLY!EquilibriaInvolvingAWeakAcidCalculatethepHofa0.0010Msolutionofformicacid,HCO2H.HCO2H+H2OHCO2-+H3O+Ka=1.8x10-4

Approximatesolution

[H3O+]=4.2x10-4M,

pH=3.37ExactSolution

[H3O+]=[HCO2-]=3.4x10-4M [HCO2H]=0.0010-3.4x10-4=0.0007M

pH=3.47HONORSONLY!EquilibriaInvolvingAWeakBaseYouhave0.010MNH3.Calc.thepH. NH3+H2ONH4++OH-

Kb=1.8x10-5Step1.

Defineequilibriumconcs.inICEtable [NH3] [NH4+] [OH-]initial change equilib 0.010 0 0-x +x +x0.010-x x xHONORSONLY!EquilibriaInvolvingAWeakBaseYouhave0.010MNH3.Calc.thepH. NH3+H2ONH4++OH-

Kb=1.8x10-5Step1.

Defineequilibriumconcs.inICEtable [NH3] [NH4+] [OH-]initial change equilib 0.010 0 0-x +x +x0.010-x x xHONORSONLY!EquilibriaInvolvingAWeakBaseYouhave0.010MNH3.Calc.thepH. NH3+H2O

NH4++OH-

Kb=1.8x10-5Step2.

Solvetheequilibriumexpression

Assumexissmall,so x=[OH-]=[NH4+]=4.2x10-4Mand[NH3]=0.010-4.2x10-4≈0.010MTheapproximationisvalid !HONORSONLY!EquilibriaInvolvingAWeakBaseYouhave0.010MNH3.Calc.thepH. NH3+H2ONH4++OH-

Kb=1.8x10-5Step3.

CalculatepH[OH-]=4.2x10-4MsopOH=-log[OH-]=3.37BecausepH+pOH=14,pH=10.63HONORSONLY!TypesofAcid/BaseReactions:SummaryHONORSONLY!pHtestingThereareseveralwaystotestpHBluelitmuspaper(red=acid)Redlitmuspaper(blue=basic)pHpaper(multi-colored)pHmeter(7isneutral,<7acid,>7base)Universalindicator(multi-colored)IndicatorslikephenolphthaleinNaturalindicatorslikeredcabbage,radishesPapertestingPapertestslikelitmuspaperandpHpaperPutastirringrodintothesolutionandstir.Takethestirringrodout,andplaceadropofthesolutionfromtheendofthestirringrodontoapieceofthepaperReadandrecordthecolorchange.Notewhatthecolorindicates.Youshouldonlyuseasmallportionofthepaper.Youcanuseonepieceofpaperforseveraltests.pHpaperpHmeterTeststhevoltageoftheelectrolyteConvertsthevoltagetopHVerycheap,accurateMustbecalibratedwithabuffersolutionpHindicatorsIndicatorsaredyesthatcanbeaddedthatwillchangecolorinthepresenceofanacidorbase.SomeindicatorsonlyworkinaspecificrangeofpHOncethedropsareadded,thesampleisruinedSomedyesarenatural,likeradishskinorredcabbageACID-BASEREACTIONS

TitrationsH2C2O4(aq)+2NaOH(aq)--->

acid

base

Na2C2O4(aq)+2H2O(liq)Carryoutthisreactionusinga

TITRATION.

Oxalicacid,H2C2O4SetupfortitratinganacidwithabaseTitration1.Addsolutionfromtheburet.2.Reagent(base)reactswithcompound(acid)insolutionintheflask.Indicatorshowswhenexactstoichiometricreactionhasoccurred.(Acid=Base)ThisiscalledNEUTRALIZATION.35.62mLofNaOHisneutralizedwith25.2mLof0.0998MHClbytitrationtoanequivalencepoint.WhatistheconcentrationoftheNaOH?

LABPROBLEM#1:StandardizeasolutionofNaOH