BasicChemistry—Mid-termExam 1

Name:________________________________

Studentnumber:_______________________

AutumnSemester

BasicChemistryforEngineering/FundamentalInorganicChemistry

Mid-termExam

07December2015

Time:60minutes

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

BasicChemistry—Mid-termExam 2

EquationsandData

pV=nRTwherep=pressure,V=volume,n=no.ofmolesofgas,R=8.3144JK–1mol–1orR=0.082057LatmK–1mol–1,T=temperatureinKelvin0˚C=273KAvagadroconstant6.022x1023mol–1pH=–log10[H+]PartialpressureofCO2inairatsealeveland25.0°C:0.000390atmSolubilityofCO2inH2Oat25.0°C:0.14gper100mlH2O.Commonoxidationstates:H:+1,O:–2,Halogens:–1,Group1metals:+1,Group2metals:+2.Otherelementsarevariable.MaximumvapourpressureH2Oat 12.0°C:0.0193atm 22.0°C:0.0690atm 25.0°C:0.0789atmTableofelectronegativities

BasicChemistry—Mid-termExam 3

BasicChemistry—Mid-termExam 4

Question1A)Ageologistproposesusingironoxide(Fe2O3)toloweratmosphericcarbondioxidelevelsbythereaction:

Fe23+O32–+CO2+Li→Fe2+(CO3)2–+Li+O2–

i) This reaction contains mistakes. Write a properly balanced equation below:

[2] ii) Choose one word that best describes this reaction from the following list:

Redox, Displacement, Bronsted-Lowry acid/base, Combination, Dissociation ___________________

[1] iii) A chemist performs a test on the reaction in part i) using a 1.00 L sealed, metal cylinder filled with air at 1.00 atm pressure and 25.0 °C. If she reacts 5.00 g of Fe2O3 with the CO2 of the air inside the cylinder, will all of the CO2 be consumed? ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________

[6] iv) What will the final total gas pressure be inside the cylinder? (Note Fe2O3 and Fe(CO3) are solids, their contribution to pressure is insignificant). ________________________________________________________________________________

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BasicChemistry—Mid-termExam 5

Question2A)Carbondioxide(CO2)reactswithwater(H2O)tomakecarbonicacid(H2CO3).i)Writeabalancedequationforthisreaction:

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ii)Assumingthatcarbonicaciddissociatescompletelyinwater,writeabalancedequationforthedissociationofcarbonicacidinwater.

[1]iii)Whatkindofacidiscarbonicacid?___________________________

[1]iii)Achemistleaves1.00Lofdistilledwateropentotheairat25.0°Covernight.Thenextday,hefindsthepHhasdroppedbelow7.0.WhatisthenewpHofthewater,assumingthedropinpHisduetodissolvedCO2?(useyourequationsfromabove)________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________

[6]iv)Inreallife,thismuchCO2doesnotmakewaterveryacidic.Explainwhythisis.________________________________________________________________________________

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BasicChemistry—Mid-termExam 6

Question3A)Bauxiteisakindofrockthatcontainsalargeproportionofaluminiumoxide(Al2O3).Thealuminiumoxideispurifiedfrombauxiteandthendissociatedintoaluminium(Al)andoxygen(O2)byastrongelectriccurrent.Usethewords‘element’,‘compound’,or‘mixture’todescribei)bauxite,___________________________ii)aluminiumoxide,___________________________

[2]iii)WhatisthemostlikelyoxidationstateofAlinAl2O3?________________________________________________________________________________

[1]vi)Assumingthisisthemostfavouredoxidationstateofaluminium,doyouexpectaluminiummetal(Al0)tobeagoodoxidisingagentoragoodreducingagent?Why?________________________________________________________________________________ ________________________________________________________________________________

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v)IsAl2O3mostlikelytobeanioniccompound,acovalentcompoundorsomewhereinbetween?Why? ________________________________________________________________________________ ________________________________________________________________________________

[2]vi)AstudentbelievesAl2O3isacovalentcompoundanddrawsaLewisdiagramtodemonstrateherreasoning.Giventhatthethreeoxygenatomsareeachbondedtobothaluminiumatoms,drawasuitableLewisdiagramofAl2O3.

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vi)Doesthiscompoundobeytheoctetrule?Why?________________________________________________________________________________

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BasicChemistry—Mid-termExam 7

Question4A)i)Thediagrambelowshowsaneutralatom.Labelthediagram

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iii)Whichelementisthis?___________________________

[1]Thiselementmakescompoundswithsodium(Na)oftheformNaX3(Replace‘X’withtheappropriatechemicalsymbol).Howmuchofthiselement(grams)wouldyouneedtomake15.0gofNaX3?________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________

[4]

AssumethatallatomsinNaX3areionised.GiventhatXhastwodifferentoxidationstatesinthiscompound,writeacceptableoxidationstatesforallionsintheform:Nan,Xn,Xn,Xn(e.g.forH2OyouwouldwriteH+,H+,O2–)(Note:morethanoneanswerispossible,chooseonecombination)________________________________________________________________________________

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BasicChemistry—Mid-termExam 8

Question5A)Humidityisameasureoftheactualvapourpressureofwaterasapercentageofitsmaximumpossiblevapourpressureatagiventemperature.i)Acomfortablehumidityistypically50%.Whatpartialpressureofwatervapourdoesthiscorrespondtoat25.0°C?________________________________________________________________________________

[1]ii)Onacoldday(12.0°C),apersonnotesthehumidityoftheirroomis50%.Theyturnontheirheaterandheattheroomto22.0°C.iii)Assumingnosignificantevaporationofwater,whatwillhappentothehumidityoftheroom?Why?________________________________________________________________________________

[2]iv)Giventhatthecomfortablerangeofhumidityis40—60%,willtheroombetoodry,comfortableortoohumid?________________________________________________________________________________ ________________________________________________________________________________

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B)Achemisttakesa1.00Lcontaineranda2.00Lcontainer,bothhalf-filledwithwater.The1.00Lcontainerissealedwithairintheemptyspaceatatmosphericpressure(1.00atm)andat25.0°C.The2.00Lcontainerissealedwithairat10.0atmpressure.At25.0°C,whatwillthevapourpressureofwaterbe:i) inthe1.00Lcontainer?___________________________ inthe2.00Lcontainer?___________________________

[1]ii)Whatwillthetotalpressurebeinthe1.00Lcontainer?___________________________Whatwillthetotalpressurebeinthe2.00Lcontainer?___________________________

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iii)Howmanymolesofwaterwillbeinthevapourphaseinthe2.00Lcontainer?

________________________________________________________________________________ ________________________________________________________________________________

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BasicChemistry—Mid-termExam 9

RoughWorking