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.