BasicChemistry—FinalExam 1

Name:________________________________

Studentnumber:_______________________

AutumnSemester

BasicChemistryforEngineering/FundamentalInorganicChemistry

FinalExam

3February2014

Time:60minutes

Instructions:Answerany4questionsoutof5possiblequestions.Youmayanswermorethan4questionsifyouwish.Yourmarkswillbetakenfromyourtop4questions.Showallrelevantworking.Writeallanswersandfinalworkinginpen.Giveyouranswerstoanappropriatenumberofsignificantfigures.9pagesincluding:1toppage,1datapage,1periodictable,5questionpages,1pageforroughworkingHandinallpagesattheendoftheexam.Permissiblematerials:Calculator.EnglishorEnglishbilingualDictionary.

BasicChemistry—FinalExam 2

EquationsandData

Avagadronumber6.022x1023pV=nRTwherep=pressure,V=volume,n=no.ofmoles,R=idealgasconstantT=temperatureR=8.3144JK–1mol–1orR=0.082057LatmK–1mol–1Totalheatreleased/gainedbyreaction=∑∆Hfproducts–∑∆Hfreactants∆HfCO2(g)=–393kJmol–1∆HfCH4(g)=–74.9kJmol–1∆HfH2O(g)=–242kJmol–1Density37%formaldehyde(HCHO)solution:1.01gml–1

BasicChemistry—FinalExam 3

Andrew Robertson� 31/1/14 8:49 AMComment: Clearerblack/whiteperiodictable

BasicChemistry—FinalExam 4

Question1A)i)Circlethemetalsthatareusefulforbeingcorrosionresistant.

ironcopperaluminiumtincalciummanganese

[1]

ii)Choosetwometalsfromtheabovelistandexplainhowtheyresistcorrosion.

Tinresistscorrosionbecauseitisunreactive.Aluminiumresistscorrosionbecauseitformsa

protectivelayerofoxideonitssurface.

[4]

B)Tin(Sn)hastwopossiblecrystalstructuresatnormalpressures:themetallicβ-formanda

brittle,non-metallicα-form.

i)Whichformwillbeapoorconductorofheat?

Theα-form

[1]

Consultthephasediagrambelow.Willtinbeagood

choiceofmetal

ii)foroutsideelectricalapplicationsinthemiddleofthePacificOcean?Why?

ItwillbeagoodchoiceofmetalinthePacificOceanbecauseitresistscorrosion.

iii)AndattheSouthPole?Why?

ItwillnotbeagoodchoiceattheSouthPolebecauseitwilltransformtotheα-form.[4]

Andrew Robertson� 28/1/14 11:19 AM

Andrew Robertson� 28/1/14 11:20 AM

Comment: OnemarkforeachCauseandeffectcomment.

Comment: Twoforcorrectyes/no,twoforcorrectreasoning.

BasicChemistry—FinalExam 5

Question2

A)AninventorsayshehasinventedacatalystthatmakesCO2reactwithwatervapourtogive

offheatandgenerateCH4andO2aswasteproducts.

i)Writeabalancedequationforthisreaction.

CO2+2H2O——>CH4+2O2

[1]

ii)Withoutacatalyst,canCO2beusedtogenerateheataccordingtothisreaction?Usedata

fromthedatasheettoexplainyouranswer.

∆Hrxn=(–74.9kJmol–1+0kJmol–1)–(–393mol–1+2(–242kJmol–1))=802kJmol–1

Thisreactionisendothermicsoitcannotbeusedtogenerateheat.

[2]

iii)DoesusingacatalystenableCO2tobeusedtogenerateheat?Why?

No.Catalystsdonotchangethethermodynamicsofareaction.

[2]

iv)AnotherinventorhasmadeacatalystthatwillturnCO2andwatervapourintoCH4andO2

whenheatisaddedfromoutside.Giveonereasonwhyacatalystmightbenecessaryforthis

reaction.

Thereactionwillbetooslowwithoutacatalyst.(Theactivationenergyistoohighwithouta

catalyst).

[1]

B)i)Explain,intermsofcollisiontheory,whyraisingthetemperatureofareactionincreases

therateofreaction.

Raisingthetemperatureofareactionincreasestheproportionofreactantmoleculesthat

haveenoughenergyforareaction.

[2]

ii)Explain,intermsofcollisiontheory,whyusingaheterogeneouscatalystcanincreasethe

rateofreaction.

Aheterogeneouscatalystincreasesthenumberofreactantmoleculesthatmeetwiththe

correctorientationforreactionand/ordecreasestheactivationenergy,meaningmore

reactantmoleculeshaveenoughenergyforreaction.

[2]

Andrew Robertson� 28/1/14 5:21 PMComment: Need∆Hfforthesecompounds.Hasthiscalculationappearedinthenotes/setproblems?Putbasicformulaindatasheet.

BasicChemistry—FinalExam 6

Question3A)Alaboratorytechnicianisconstructingavoltaiccell.Whichofthefollowingcomponentsandsolutionswillsheneedtouse.Illustrateyouranswerwithadiagramofthevoltaiccell.stripofzincmetal,stripofcoppermetal,stripofplastic,woodentoothpick,wire(s),voltmeter,saltbridge,zincsulfate(Zn2+SO42–)solution,coppersulfate(Cu2+SO42–)solution,beaker(s),atap,glassbeads,lighter,battery,cottonwool

(Diagramrequires:beaker,solutions,metalstrips,voltmeter,wires,saltbridge.)

[6]

B)Giventhatcopperhasastrongeraffinityforelectronsthanzinc,writethefullequation,ionicequationandtwohalfequationsforthisreaction. Zn+CuSO4——>Cu+ZnSO4 Zn+Cu2+——>Cu+Zn2+ Zn–2e–——>Zn2+ Cu2++2e–——>Cu

[4]

Andrew Robertson� 28/1/14 3:07 PMComment: Beaker,solutions,metalstrips,voltmeter,wires,saltbridge.

BasicChemistry—FinalExam 7

Question4A)Refertothelinedrawingofamoleculebelow:i)Howmanycarbonatomsdoesthismoleculehave?17

[1]ii)Whichofthefollowingfunctionalgroupsappearonthismolecule?Circlethefunctionalgroupsonthelinedrawingandwritethenamenexttothecircle.benzenering,doublebond(notaspartofotherfunctionalgroups),alcohol(notaspartofotherfunctionalgroups),amine,nitro,ether,carboxylicacid,ketone,halide

[4]

iii)Showonthediagramoneplacewhereyouwouldexpecttofindresonanceandoneplacewhereyouwouldexpecttofindstronginductiveeffects.(Note,theremaybeotheranswers)

[2]B)i)Drawtwoconstitutionalisomersofthefollowingmolecule:

[2]

ii)Drawoneconfigurationalisomerofthefollowingmolecule:

[1]

O

NH2

N

S

O

CH3

CH3

OH

O

benzene ring

resonance

inductive effects

amine

ketone

carboxylic acid

OH OH OH

Andrew Robertson� 28/1/14 4:01 PM

Andrew Robertson� 28/1/14 4:02 PM

Andrew Robertson� 5/2/14 11:25 AM

Comment: Similartobenzylpenicillinbutamidechangedtoketoneandamineforsakeofquestion.

Comment: Oneforeachf.g.

Comment: Thesetwotermswereincorrectlyswitchedontheactualexam

BasicChemistry—FinalExam 8

Question5

A)i)Astudentaccuratelymeasurestheboilingpointoftapwaterandfindsittobe101˚C.

Whatisthemostlikelyexplanationforthishighboilingpoint?

Impuritiesinthewaterhaveraisedtheboilingpointofthewater.

[1]

ii)Fishcanhavedifficultybreathingatelevatedtemperatures.Whatisthemostlikely

explanationforthisproblem?

Thereislessdissolvedoxygeninhighertemperaturewater.

[1]

B)i)Anaqueoussolutionofformaldehyde(HCHO)islabelledasbeing37%byweight.What

istheconcentrationofthissolutioninmolarunits(M)?(refertothedatasheetfornecessary

information)

1dm337%HCHOsolutionweighs1000mlx1.01gml–1=1010g

massofHCHO=1010gx0.37=373g

MrHCHO=2(1.01gmol–1)+12.0gmol–1+16.0gmol–1=30.0gmol–1

373g÷ 30.0gmol–1=12.5mol(12.45mol)

Molarity=12moldm–3(12moldm–3isacceptable)

[3]

ii)Giventhatformaldehydeisagas,shouldthesolutionbestoredatloworhightemperatures

tomaintainitsmaximumconcentration?Why?

Formaldehydesolutionshouldbestoredatlowtemperaturesbecausegasesarelesssoluble

athightemperatures.

[2]

iii)Couldthissolutionbestoredat–1˚Candstillbereadyforimmediateuseasaliquid?Why?Yes,becausethesolutewilllowerthefreezingpointofthesolvent(water).

[2]iv)Ifthesolutionpartiallyfroze,whatwouldhappentotheconcentrationofformaldehydein

theremainingliquid?

Itwouldincrease.

[1]

Andrew Robertson� 28/1/14 5:06 PMComment: Needmoldm–3ondatasheet.

BasicChemistry—FinalExam 9

RoughWorking