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Lecture03,WednesdayofWeek2 today:finishChapter13 FridayinRecitation:

Quiz2, diagnostictestbringyourlabtop/tablet

Laboratory:ExploringPolymers(continued) FirstExam:

Wednesdayevening,Feb.11,6:45 7:45pm putawayalldistractions setyourclickertoChannel17or27

SItimesforCHEM178 Sundays,4:10pm@Pearson1105 Prina Mondays,5:10pm@Sweeney1116 Lindsey Tuesdays,2:40pm@Sweeney1116 Lindsey Tuesdays,5:10pm@Carver0068 Elizabeth Tuesdays,6:10pm@Pearson1105 Prina Wednesdays,5:10pm@Pearson1105 Prina Wednesdays,6:10pm@Carver0068 Elizabeth Thursdays,1:10pm@Sweeney1116 Lindsey Thursdays,7:10pm@Carver0068 Elizabeth

MCassignments pastdueassignments:

ECIntroduction ECReview LT03:Lecture3Tutorial

availableassignments: HWCh13: due1/24atmidnight LT04 due1/26at1pm LT05 due1/28at1pm

upcomingassignments: LT06 due2/2at1pm LT07 due2/4at1pm HWCh15 due2/7atmidnight

RecitationThisFriday(Jan.23): BringalaptoportabletwithWiFicapabilitiestoclass

therewillbeanonlinediagnosticreviewtestatthebeginningofclass

youwillgetparticipationpoints ifyoudonthavealaptop/tablet,youcantakethetestonpaper

thisispartofagraduatestudentstudy

Review

Solubilityasafunctionof temperature pressure(especiallyforgasses) HenrysLaw

likedissolveslike saturatedsolutionsanddynamicequilibrium concentrationunits

molefraction,molarityandmolality percentbymass,ppm,andppb howtoconvertbetweenunits

IhavereadCh.13toend beforeclass.1. yes2. no3. someofit4. mostofit5. Weneedtoreadfor

thisclass?!?

1. 2. 3. 4. 5.

0 0 000

10

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Thecorrectformulaforchloricacidis:

1. HCl(aq)2. HClO(aq)3. HClO2(aq)4. HClO3(aq)5. HClO4(aq)

1. 2. 3. 4. 5.

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25

6

122

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ChangingMolaritytoMolality molarity:mol/L,amountpervolumesolution molality:mol/kg,amountpermasssolvent needtoconvertvolumeofsolutiontomassofsolvent

strategy: densityofsoluon:volumemasssoluon molarmasssolutemasssolute masssoluonmasssolvent

Calculate the molality of a 48.0% (by mass) aqueous solution of hydrobromic acid

(FW = 80.9 g/mol).

A. 0.48B. 5.93C. 8.90D. 11.4E. Thedensityofthesolutionis

neededtosolvetheproblem.

A. B. C. D. E.

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71

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87

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How to calculate

2

HBr 0.480 (HBr )mass

mass H O

Assume you have 1 kg of solution

mass of HBr = 0.480 kg or 480 g

moles of solute 5.93 11.41 solvent 0.520

molmolality mkg kg

mol of HBr = 480 g / 80.9 g/mol = 5.93 mol

HBr 0.4801

masskg

mass of solvent = 1.000 kg 0.480 kg = 0.520 kg

mass of solute%(by mass) 100%mass of solution

13.5ColligativeProperties Somepropertiesofsolventschangewhensolutesareadded: VaporPressure decreases Meltingpoint decreases Boilingpoint increases Osmoticpressure changes

Thechangesdependonthenumberofsoluteparticles

Usefulfor determiningmolarmasses technicalandmedicalapplications

effectofsoluteonvaporpressure:

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usingknowledgeaboutelectrolytes: 1.0M solutionofanelectrolyte:

ioniccompoundMnYm dissociates inton cationsandm anions n+mmolparticles insolution

1.0M solutionofanonelectrolyte: molecularsolute 1mol particles insolution

vaporpressureofasolution Raoults Lawforidealsolutions:

nonvolatilesoluteinvolatilesolventPsolution =Xsolvent Psolvent

X isthemolefraction idealmixtureoftwovolatilecomponents:

PA =XA PAPB =XB PBPtot =PA +PB

ForwhichaqueoussolutiondoyouexpectthehighestvaporpressureofH2O?

A. 0.1m glucoseB. 0.1mNaClC. 0.1msodiumacetateD. 0.1maceticacid

A. B. C. D.

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Psolution = Xsolvent Psolvent ; X = mole-fraction

FreezingPointDepression proportionaltothemolality ofthesolution(amountofsolute):

Tf =Kf m Tf =Tf(solvent) Tf(solution) positivequantity Kf =molal freezingpointdepressionconstant

- apropertyofthesolvent.

BoilingPointElevation proportionaltothemolalitym ofthesolution(amountofsolute):

Tb =Kb m Tb =Tb(solution) Tb(solvent) positivequantity Kb =molal boilingpointelevationconstant

apropertyofthesolvent.

UsingPhasediagramstoseeBoilingPointElevation andFreezingPointDepression

blacklines:puresolvent bluelines:solution normalboilingpointat

1atm (horizontalline) normalmeltingpointat

1atm (horizontalline)

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Forwhichaqueoussolutiondoyouexpectthehighestboilingpoint?

A. 0.100m NaIB. 0.100m Ba(NO3)2C. 0.100m KBrD. 0.100m FeSO4

A. B. C. D.

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Realsolutions:vant Hofffactor

Comparefreezingpointdepressionof 1m solutionofNaCl 1m solutionofglucose effectisnot exactlydouble.

somesolvatedNa+ andCl ionswillreassociateforashortperiodoftime,

vant Hofffactor,i:numberoffreeparticlesperformulaunitofsolute

vant HoffFactor adjustedequations: reassociationismorelikelyathigherconcentration. thenumberoffreeparticlespresentisconcentrationdependent.

Tb =Kbm i Tf =Kf m i

molarmassesfromfreezingpointdepression

1.0gofanunknownorganic(nonelectrolyte) 10.0gofnaphtalene

m.p.80.26C Kf =7.45C/m measuredmeltingpoint:T=76.17C whatisMMoftheunknown? Tf =80.26C 76.17C =4.09C Tf =Kf m m =0.549mol/kg solvent concentrationofsolutionisalso: (1.0g(solute)/MM)/0.010g(solvent)=0.549mol/kg solveforMM: MM=(1.0g/0.010kg)x(1kg/0.549mol)=182g/mol

Osmosis

= ( )RT=MRTnV

M = molarity

Osmosisinbloodcells Isotonicsolutions:

theconcentrationisthesameonbothsidesofamembrane(i.e.,noosmoticpressure)

hypertonicsolution: thesoluteconcentrationoutsidethecellisgreaterthanthatinsidethecell,theoutsidesolutionishypertonic.

Waterwillflowoutofthecell,andcrenation results. hypotonicsolution:

thesoluteconcentrationoutsidethecellislessthanthatinsidethecell,theoutsidesolutionishypotonic.

Waterwillflowintothecell,andhemolysis results.

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OsmosisinbloodcellsWhatsAhead:

Studyonyourown: p.536Osmosis p.541Colloids(nanochemistry)

Nextlecture(MondayJan.26)startsChapter15:ChemicalEquilibrium