Do-Now:1.   Potassiumchlorideisdissolvedinwater.Diagram

whatthiswouldlooklikeonapieceofpaper,usingspherestorepresentatoms.Indicatecharges.

2.   Whatisanelectrolyte?3.   IdenAfyanddescribefourproperAesofwater4.   Inabiochemicalassay,achemistneedstoadd

3.81gofglucosetoareacAonmixture.CalculatethevolumeinmLofa2.53MglucosesoluAonsheshouldusefortheaddiAon.

TurninyourlabsJ2

Announcements• Newdojopoints!•  DaylightsavingsthisSunday•  StudyCh.4!

CW/HWAssignments3.  Ch.4NotesPartB4.  PracGceProblemsPacket

PLANNER •  Finishpacket•  Addallstandardstounitlog

EssenGalknowledgestandards•  2.A.3:SoluGonsarehomogeneousmixturesinwhichthephysicalproperGes

aredependentontheconcentraGonofthesoluteandthestrengthsofallinteracGonsamongtheparGclesofthesolutesandsolvent.

•  2.B.2:DipoleforcesresultfromtheaNracGonamongtheposiGveendsandnegaGveendsofpolarmolecules.Hydrogenbondingisastrongtypeofdipole-dipoleforce.

•  2.B.3.:IntermolecularforcesplayakeyroleindeterminingtheproperGesofsubstances,includingbiologicalstructuresandinteracGons.

•  3.A.1:Achemicalchangemayberepresentedbyamolecular,ionic,ornetionicequaGon.

•  3.B.1:SynthesisreacGonsarethoseinwhichatomsand/ormoleculescombinetoformanewcompound.DecomposiGonisthereverseofasynthesis,aprocesswherebymoleculesaredecomposed,oSenbytheuseofheat.

•  3.B.3:InoxidaGon-reducGonreacGons,thereisanettransferofelectrons.•  6.C.3:Thesolubilityofasubstancecanbeunderstoodintermsofchemical

equilibrium.

FLT•  Iwillbeableto:–  Drawand/orinterpretrepresentaGonsofsoluGonsthatshowtheinteracGons

betweenthesoluteandsolvent–  ExplainobservaGonsregardingthesolubilityofionicsolidsandmoleculesin

waterandothersolventsonthebasisofparGcleviewsthatincludeintermolecularinteracGonsandentropiceffects

–  TranslateanobservedchemicalchangeintoabalancedchemicalequaGonandjusGfythechoiceofequaGontype(molecular,ionic,netionic)intermsofuGlityforthegivencircumstances

–  ExplaintherelaGvestrengthsofacidsandbasesbasedonmolecularstructure,interparGcleforces,andsoluGonequilibrium

–  Designand/orinterpretdatafromanexperimentthatusesgravimetricanalysisorGtraGontodeterminetheconcentraGonofananalyteinasoluGon

–  IdenGfycompoundsasBronsted-Lowryacids,bases,and/orconjugateacid-basepairs,usingproton-transferreacGons

–  IdenGfyredoxreacGonsandjusGfytheidenGficaGonintermsofelectrontransfer

–  Designand/orinterprettheresultsofanexperimentinvolvingredoxGtraGon•  Bycomple1ngCh.4Notes

Ch.4:TypesofRxns&SoluAonStoichiometry

Recall

Overview• WecancategorizereacGonsintosomegeneraltypes:– CombinaGon/Synthesis– DecomposiGon– CombusGon– RedoxReacGons– Singledisplacement/replacement– Doubledisplacement/replacement

• PrecipitaGonReacGon• Acid-Base/NeutralizaGon

DoubleReplacementRxns•  PrecipitaGonReacGons

– WhentwosoluGonsofsolublesaltsarecombinedandaninsolublesaltinaqueoussoluGonisformed

– Theinsolublesaltthatformsisknownastheprecipitate

DoubleReplacementRxnsPb(NO3)2(aq)+2KI(aq)àPbI2(s)+2KNO3(aq)

Molarity •  Molarity(M)=molarconcentraGon=thenumberofmolesofsoluteperliterofsoluGon

DiluGon

DiluGon•  ConcentratedsoluGonsareoSenusedas“stock”soluGons

•  ThesecanbedilutedtopreparealessconcentratedsoluGon

DiluGon

DiluGon•  Equipmentinvolved:

– Pipet/PipeNe–toaccuratelymeasureandtransferagivenvolumeofsoluGon.Maybemeasuring(gradaGon)orvolumetric(onlyasinglemeasurementvalue)

DiluGon•  Ex/Describehowyouwouldprepare5.00x102mLofa1.75MH2SO4soluGon,starGngwithan8.61MH2SO4stocksoluGon

First:M1= M2=V1= V2=

DiluGon•  Ex/Describehowyouwouldprepare5.00x102mLofa1.75MH2SO4soluGon,starGngwithan8.61MH2SO4stocksoluGon

First:M1=8.61M M2=1.75MV1=? V2=5.00x102mLSecond:PlugintoM1V1=M2V2

DiluGon•  Trythis:•  Whatvolumeof16Msulfuricacidmustbeusedtoprepare1.5Lofa0.10MH2SO4soluGon?

PrecipitaGonReacGons

PrecipitaGonReacGons•  PrecipitaGonreacGonsoccurinaqueoussoluGonandresultintheformaGonofaninsolubleproduct(precipitate)

•  Ex/Pb(NO3)2(aq)+2KI(aq)àPbI2(s)+2KNO3(aq)

PrecipitaGonReacGons•  WeoSenseparatetheprecipitatefromthesoluGonbyfiltraGonusinggravimetricanalysis(moreonthismomentarily)

PrecipitaGonReacGons•  SolubilityRulesàyouarenotrequiredtomemorizethesefortheAPexam,justusethem

Ø MostalkalimetalsaltsandNH4+saltsaresoluble

Ø Cl-,Br-,I-aresoluble(exceptforAg+,Hg22+,Pb2+)Ø F-aresoluble(exceptforIIAmetals)Ø NO3

-,ClO3-,ClO4

-,andCH3COO-aresolubleØ SO4

2-aresoluble(exceptforCa,Sr,Ba,Ag+,Pb2+,Hg22+)

Ø CO32-,PO4

3-,C2O42-,CrO4

2-,S2-,OH-,andO2-areinsoluble(exceptforcaseswithrule#1)

Ø Itcanbeassumedthatsaltsthatdissolveinwaterarestrongelectrolytes

PrecipitaGonReacGons•  Wecanpredictwhetherornotprecipitateswillformusingsolubilityrules

•  Ex/Whatprecipitate(ifany)willformifthefollowingpairsofsoluGonsaremixed?a.  KNO3andBaCl2b.  Na2SO4andPb(NO3)2c.  KOHandFe(NO3)3

DescribingRxnsinSoln’

RxnsinSoln’s•  WecandescribereacGonsinsoluGonsafewdifferentways:

§  CompletebalancedequaGon•  ThisistheoverallreacGon

§  CompleteionicequaGon•  Thisrepresentsallsolublecompounds/electrolytesasions

§  NetionicequaGons•  Spectatorions(ionsthatdidnotchangeorwerenotinvolved)areexcludedandonlythosesoluGoncomponentsundergoingachangeareincluded

RxnsinSoln’s•  Example:Aqueouspotassiumchlorideisaddedtoaqueoussilvernitratetoformasilverchlorideprecipitateplusaqueouspotassiumnitrate.

RxnsinSoln’s•  Example:Aqueouspotassiumhydroxideismixedwithaqueousiron(III)nitrate

GravimetricAnalysis

GravimetricAnalysis•  Gravimetricanalysis=analyGcaltechniqueusedtodeterminetheconcentraGonofananalyte(anionbeinganalyzed)byprecipitaGngtheionasaninsolublesalt,whichcanthenbemassed

GravimetricAnalysis•  Typically,itinvolvestheformaGon,isolaGon,andmassdeterminaGonofaprecipitate

1.  Determinetheanalyte/ionyouneedtoprecipitate2.  ChooseareacGonthatwillproduceaninsolublesalt

thatcontainsthation3.  PerformaprecipitaGonrxntocompletelyprecipitate

thetargetionàbesuretoaddexcessoftheothersoluGontoensurecompleteprecipitaGon(otherwiseyourconcentraGonwillbeinaccurate)

4.  Carefully,filter,wash,anddrytheprecipitate5.  Takethemass6.  UsestoichiometrytofigureoutyourconcentraGon

33

GravimetricAnalysis•  Ex/Astudentwantstodetermine[Ba+2]in100.00mLofanunknownsoluGonofBa+2.Shedecidedtoprecipitatethebariumionsasbariumsulfate,aninsolublesalt.SheaddsanexcessofsodiumsulfatesoluGontothebariumsoluGonunGlnomoreprecipitateforms.Shethenfilters,washes,anddriestheprecipitate.Shemeasuresthemasstobe2.917g.Determine[Ba+2]inthesoluGon.

GravimetricAnalysis•  First,assembleyourknowninformaGon•  Vsoln=100.00mL MassBaSO4=2.917g•  Second,writeyourbalancednetionicequaGon:

Ba2+(aq)+SO42-(aq)àBaSO4(s)

•  Third,usestoichiometrytodeterminethemolofyouranalyte(Ba2+)

•  Lastly,dividebyvolumeofyoursoluGontogetmolarity

GravimetricAnalysis•  Filters,washes,anddriestheppt,andmeasuresitsmasstobe2.917g

•  WritetheequaGon:•  Ba+2(aq)+SO4

2-(aq)àBaSO4(s)

•  MakesuretheequaGonisbalanced•  Convert2.917gBaSO4tomolofBa2+

•  DividebythevolumeofsoluGontogettheconcentraGon

GravimetricAnalysis•  Trythis:•  25.00mLofalead(II)nitratesoluGonistreatedwithexcessaqueoussodiumsulfate.ASerfiltraGonanddrying,0.303gofsolidleadsulfateisisolated.WhatwastheconcentraGonofthelead(II)nitratesoluGon?

GravimetricAnalysis•  Trythis:A0.5662-gsampleofanioniccompoundcontainingchlorideionsandanunknownmetalisdissolvedinwaterandtreatedwithanexcessofAgNO3.If1.0882gofAgClprecipitateforms,whatisthepercentbymassoftheoriginalcompound?

•  Hint,%Cl=massofCl/0.5662gsamplex100%

CW•  QuesGonpacket

– ShowALLstepsclearly•  StudyCh.4