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INDUSTRIALCHEMISTRYNOTES–ROHANBARAR2016

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IndustrialChemistryNotesSection1Industrialchemistryprocesseshaveenabledscientiststodevelopreplacementsfornaturalproducts

• Discusstheissuesassociatedwithshrinkingworldresourceswithregardtooneidentifiednaturalproductthatisnotafossilfuel,identifyingthereplacementmaterialsusedand/orcurrentresearchinplacetofindareplacementforthenamedmaterial

• Identifydata,gatherandprocessinformationtoidentifyanddiscusstheissuesassociatedwiththeincreasedneedforanaturalresourcethatisnotafossilfuelandevaluatetheprogresscurrentlybeingmadetosolvetheproblemsidentifiedØ Shrinkingworldresourcesaredueto:

§ Increaseindemand§ Inabilityforthenaturalresourcetomeet

demand

§ Depletionofthenaturalresource§ Economiccompetition,increasingprices§ EnvironmentalIssues

Ø Naturalproductsinclude§ NaturalRubber§ Wood§ Wool

§ Ivory§ Soap§ Fertiliser

Theincreasingpopulationoftheworldisleadingtogreaterdemandonallnaturalresources,andastheyarebeingdepleted,syntheticalternativesmuchbefound.Onesuchresourceisrubber.

Ø Naturalrubberisobtainedfromthesapoftherubbertree

(Latex)(Polyisoprene)Ø Anincisionismadeintothebarkofatree,andlatexsap

collectedandrefinedintousablerubberØ Itisapolymerof2-methyl-1,3-butadieneØ Rubberisusedtomanufacturetyres,belting,hoses,tubing,insulators,valvesandfootwearØ Thisisbecauserubberiselastic,tough,impermeable,adhesive,easilymouldableandanelectricalinsulator

Ø Naturalrubbermustundergoprocessingsoitsflexibilityandsolidityarepreservedinallconditionso Softeningbymastication(passingrubberbetweenrollers)o Grindinganddissolvinginasuitablesubstanceforcompoundingwithother

ingredientse.g.fillers,pigments,antioxidants,plasticiserso Sheetingandextrusionintovariousshapeso Vulcanisation(heatingofrubberwithsulfurinordertocrosslinkpolymerswith

sulfur)tomakeitelastic,hard,andlesssusceptibletochemicals(asshownonright).(Crosslinkingcausestherubbertospringbackintoshapewhenstretched)

Ø Limitsofnaturalrubbero Perishwhenexposedtowearo Softwhenwarm,brittlewhencoldo Hastobevulcanised(crosslinkedwithsulfur)

Ø Untilthe1940s,rubbertreesweretheprimarysourceofrubber,especiallytreesintropicalareassuchas

MalayaandBurma.

Twosignificanteventscauseddemandfornaturalrubber• TheCommercialisationoftheAutomobile

o Aftertheautomobilewasinventedtherewashighdemandforrubberforthetyresaswellasvariousothercomponentsofthecar

o Asnaturalrubbercouldnotmeetdemands,syntheticrubberwasdeveloped


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• TheSecondWorldWaro TheconflictofWorldWarIIinterruptednaturalrubbersupplies,andalsocausedanincreasein

demand(formilitaryvehicletyres)o GermanandUSscientistsdevelopedsyntheticpolymerstoreplacerubbero AfterWWII,thedemandforrubbercouldnotbemetbynaturalrubbertreeplantations,andthus

syntheticrubbersdominatedthemarketinsteadØ ThefirstsyntheticrubbertobedevelopedwasNeoprene(Polychloroprene)Ø ThispolymerwasflameretardantandhadsuperiorstrengthtonaturalrubberØ Neopreneisstillinusetodayinavarietyofindustries(CivilEngineering&Aquatics)Ø Neopreneisusefulatelevatedtemperaturesandisusedforheavy-dutyapplicationssuchaswetsuits

Ø Approximately80%oftheworld’srubberproductiontodayisfromsyntheticpolymers,themostcommon

onebeingSBR(styrene-butadienerubber)Ø Thisisacopolymerofbutadieneandstyrene

Styrene Butadiene SBR

Ø Today’smostcommonsyntheticrubberisSBR,madefromtwomonomers:butadiene(B)andstyrene(S)inthepatternBBBSBBBS(Butadiene-Butadiene-Butadiene-Styreneetc.)

Ø SBRhasalowcostanddesirablepropertiesØ Copolymeralsousedtomanufactureballs,shoesandelasticbandsØ Therawmaterialisobtainedfromcrudeoil,whichisnon-renewable.Ifcrudeoilisnotavailable,natural

rubberwillhavetobeusedtomeetthedemandordevelopabiopolymerwiththepropertiesofrubber.

Ø AdvantagesofSyntheticRubberoverNaturalRubbero Betteragingandweatheringo Greaterresistancetooil,solvents,oxygen,ozoneandcertainchemicalso Resilienceoverawidertemperaturerangeo Lesserneedforchemicaltreatmenttoassumefavourableproperties

Ø Assessment:Effective,moreversatilereplacementthatsolvesproblemsofsupplyanddemand.Attemptsto

findnon-petrochemicalalternativesformoresustainableproduction.Syntheticrubberhasbecomecheapertoproducethannaturalrubber.


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Section2Manyindustrialprocessesinvolvemanipulationofequilibriumreactions

• Explaintheeffectofchangingthefollowingfactorsonidentifiedequilibriumreactions:pressure,volume,concentrationandtemperatureLeChatelier’sprinciplestatesthatifasystematequilibriumisdisturbed,itwillmovetopartiallycounteractchangesintheconcentrationofproductsandreactants,volume,pressureandtemperatureØ Pressure

• Totalpressureissumofindividualpressuresofeachcomponentgas(NOLIQUIDSORSOLIDS)• Balancetheequation.Calculatethetotalnumberof‘moles’ofgasoneachsideofthereaction.• Increasingpressurewhenthetotal‘moles’ofreactantgassesislargershiftsequilibriumrighttowards

products(equilibriumtriestodecreasepressure)(andviceversa(decreasingpressure))• Increasingpressurewhenthetotal‘moles’ofproductgassesislargershiftsequilibriumlefttowards

reactants(equilibriumtriestodecreasepressure)(andviceversa(decreasingpressure))Ø Volume

• AnincreaseinvolumeisequivalenttoadecreaseinpressureoAdecreaseinvolumeisequivalenttoanincreaseinpressure(andviceversa)

Ø Concentration• Increasingconcentrationofreactantscausesthereversereactiontobefavoured(producingmore

products)(andviceversa)• Increasingconcentrationofproductscausestheforwardreactiontobefavoured(producingmore

reactants)(andviceversa)Ø Temperature

• EndothermicReaction–Anincreaseintemp.causesequilibriumtoshifttofavourreversereaction• ExothermicReaction–Anincreaseintemp.causesequilibriumtoshifttofavourforwardreaction• Note:Usingparticletheory/kineticenergy,increasingtemp.increasesrateofreactionforboth

• Interprettheequilibriumconstantexpression(nounitsrequired)fromthechemicalequationofequilibrium

reactionsand

• ProcessandpresentinformationfromsecondarysourcestocalculateKfromequilibriumconditionsØ PORKàProductsOverReactantsisK

Ø aA+bB cC+dD,𝐾 = [$]&['](

[)]*[+],(equilibriumconstantexpression)

Ø Whattheexpressionincludes• Allgasses• Allaqueoussolutions• Nosolidsorliquids(solvents)

Ø Theequilibriumconstantforthereversereactionisthereciprocaloftheequilibriumconstantfortheforwardreaction(1/const.)

Ø TheRICEBoxExample: N2 H2 NH3

Ratio 1 3 2Initial 0.5 0.8 0Change -0.075 -0.225 +0.15Equilibrium 0.425 0.575 0.15§ TheRICEboxcanbeusedtocalculatetheequilibriumconstantwhentheconcentration(orpartial

pressure)ofallaqueous/gaseouscomponentsisnotknown§ Writethebalancedequation,andthenfillinthe‘Ratio’rowinthetable§ Fillinallknowninformation(e.g.theinitialconcentrationofcertaincompounds)§ Usetheratiotodeterminethechange(+or–dependingonthesideoftheequation)§ Determinetheequilibriumvalues(I+C=E)andsubintotheequationforK

Ø ValueofKindicateswhereKliesinreaction• K≈1:Equilibriumdoesnotliestronglytoleftorright(middle)• K>104:Equilibriumstronglyfavoursproducts(right)–largevalue


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• K<10-4:Equilibriumstronglyfavoursreactants(left)–smallvalue

• Identifythattemperatureistheonlyfactorthatchangesthevalueoftheequilibriumconstant(K)foragivenequationØ TemperatureistheonlyfactorthatchangesK(equilibriumconstant)

• Kwillincreasewithincreasewithincreasingtemperatureiftheforwardreactionisendothermic• Kwilldecreasewithincreasingtemperatureiftheforwardreactionisexothermic(andviceversafor

both)

• Identifydata,planandperformafirst-handinvestigationtomodelanequilibriumreactionØ Method

1. Filla100mLmeasuringcylinderwithwater.LabelitA.2. Inserta2mLgranulatedpipetteandallowthewatertorise.3. Transferthisvolumeofwatertoanempty100mLmeasuringcylinder.LabelitB.4. Inserta5mLgranulatedpipetteintoBandallowthewatertoriseup.5. TransferthisvolumeofwaterbacktoA.6. MeasurethevolumesofwaterinAandB7. Thisisoncecycle.Continueuntilthevolumesstayconstant.(Willbedifferentvolumes)

Advantages Disadvantages

• Candemonstratehowareversiblereactionreachesequilibriumandthattheconcentrationremainsconstantafterequilibriumisreached

• Canalsoshowadisturbanceinconcentrationwillaffecttheequilibrium

• Clearlyseparatesreactantsandproducts(2measuringcylinders)

• Allowsanalysisoftheequilibriumconstant

• Cannotshowtheeffectoftemperature,volumeandpressureonanequilibriumreaction

• Uses2measuringcylindersinsteadofoneclosedcontainer

• Worksusingvolumesratherthanconcentrationorpartialpressures

• Chooseequipmentandperformafirst-handinvestigationtogatherinformationandqualitativelyanalysean

equilibriumreaction𝐹𝑒/0(23) + 𝑆𝐶𝑁9

(23) [𝐹𝑒 𝑆𝐶𝑁 ];0(23) + ℎ𝑒𝑎𝑡Ø Fe3+isyellow,SCN-iscolourlessØ Method

1. Mix5mLof1MFeCl3with5mLof1MNH4SCNinatesttubetogetabloodredsolution2. Dilutetoget30mLwithdistilledwateranddiluteequallyinto6testtubes3. Carryoutthefollowingtests

TestTube Test Observation Reason1 Add1mLofFeCl3 Darker [Fe3+]increaseforward2 Add1mLNH4SCN Darker [SCN-]increaseforward3 Add1mLNaForNaHPO4 Lighter [Fe3+]decreasereverse4 Heatinawaterbath Lighter Forwardisexothermic,high

tempfavoursreverse5 Coolinicebath Darker Lowtempwillfavourthe

forwardexothermicreaction

6 Control BloodRed N/A


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Section3Sulfuricacidisoneofthemostimportantindustrialchemicals

• OutlinethreeusesofsulfuricacidinindustryØ Theproductionofsulfuricacidisthelargestindustryintheworld

1. Fertiliser§ 85%ofthesulfuricacidproducedisusedtomakesolublefertiliser.§ 2NH3(g)+H2SO4(l)à(NH4)2SO4(s)

2. SteelProcessing§ Usedtoremoverustfromsteelbeforegalvanising(coatingwithtin)orpainting§ Fe2O3(s)+3H2SO4(aq)àFe2(SO4)3(aq)+3H2O(l)

3. CarBatteries§ SulfuricacidisusedastheelectrolyteinLead-Acidcarbatteries

• Describetheprocessesusedtoextractsulfurfrommineraldeposits,identifyingthepropertiesofsulfurwhich

allowitsextractionandanalysingpotentialenvironmentalissuesthatmaybeassociatedwithitsextractionØ InAustralia,themainsourceofsulfurisfromthesmeltingofcopperoreinMt.IsaØ Sulfurcanalsobeextractedfromcrudeoilandnaturalgas

Ø FraschProcess

• TheFraschProcessiscapableofextractingpureelementalsulfurfrommineraldeposits

• Themainmechanismconsistsof3concentric(onewithinanother)pipes.TheorderofthesepipesISIMPORTANT.o Superheatedwater@160°C:Meltsthedepositofsulfur.Outermostpipe.o Compressedair:Buildspressurewhichcausesthemoltensulfurtomove

upthe3rdpipe.InnermostPipe.o MoltenSulfur:Thepipethattakesthemoltensulfurfromthedeposit.

MiddlePipe.

• PropertiesofSulfurthatmakethismethodappropriateo Sulfurhasalowmeltingpointof113°C,meaningthatthesuperheated

watercanmeltito Sulfurhaslowdensity,meaningthatthecompressedaircanpushitupthe

pipeo Sulfurisinsolubleinwater,meaningitreadilyseparatesfromwaterwhen

itexitsthemoltensulfurpipe(nofurtherseparationprocessesrequired)

• EnvironmentalIssueso Sulfurisinertandnon-toxic,soitposesminimalthreattotheenvironmento Ifsulfurisoxidised,itformsSO2,whichisaleadingcauseofacidrain(asdiscussedinAcidic

Environment)o Ifreduced,itformsH2S,whichisatoxicandbad-smellinggaso Thehotwaterusedintheprocesscancausethermalpollution(LowerDissolvedOxygen,etc.)o Waterusedcanbecontaminatedwithothersubstancesfromthesulfurdeposito Theremovalofsulfurfromthegroundcausescavitiesintheground,whichcancollapseinon

themselves(GroundSubsidence).Thesearedifficulttobackfill.

• OutlinethestepsandconditionsnecessaryfortheindustrialproductionofH2SO4fromitsrawmaterials• DescribethereactionconditionsnecessaryfortheproductionofSO2andSO3• ApplytherelationshipbetweenratesofreactionandequilibriumconditionstotheproductionofSO2andSO3• Gather,processandpresentinformationfromsecondarysourcestodescribethestepsandchemistryinvolvedin

theindustrialproductionofH2SO4anduseavailableevidencetoanalysetheprocesstopredictwaysinwhichtheoutputofsulfuricacidcanbemaximisedØ TheindustrialproductionofH2SO4isknownastheContactProcess


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Ø Thereare4stepstothecontactprocess1. CombustionofSulfur

Ø S(l)+2O2(g)àSO2(g)+heatØ MoltensulfurissprayedintothefurnacetoincreasesurfaceareaØ ‘Dry’airisusedwithanoxygenlevelofabout33%

2.ProductionofSO3

Ø 2SO2(g)+O2(g) SO3(g)+heat(ΔH=-99KJ/mol)Ø Therateofreactionisincreasedby

o Increasingreactiontemperature(increasedcollisions,howeverreducesyield(LCP))o Addingporousvanadiumoxide(V2O5)catalyst(increasestherateoftheforwardandreverse

reaction)Ø ByLCP,theyieldisincreasedby

o Moderatereactiontemperatures(400-500°C)o Pressuresofabout1-2atmosphereso IncreasingtheconcentrationofO2o SO3isconstantlyremovedandcooled

Ø Tomaximiseyield,theinitialairusedcontainsabout30%–50%moreoxygenthanisrequiredØ ThisincreasedconcentrationofO2(g)forcesreactiontoright,maximisingyieldØ Thereactioniscarriedoutatabout1.5atm.Sincethereisa1.5:1ratioofgasparticles,thereactionis

alsoforcedtotherighttoreducepressure,maximisingyieldØ Theinitialgasstreamatthebeginningofthisstepisat1000°Caftercombustionofsulfur-thisistoo

hightoproduceeffectiveyieldintheexothermicreactionaboveØ Thegasstreamiscooled(heatexchanged,withheatusedtoliquefysulfurinfirststep,whichreduces

heatreleasedfromprocess)toabout550°CØ Atthislowertemperature,thegasstreampassesoverabedofV2O5catalyst,whichproducesa

relativelyrapid70%conversionofSO2toSO3.Ø Thegasstreamisthenfurthercooledto400°Candpassedoverasecondcatalyticbed,producing

overall97%conversionatthelowertemperatureØ TheremaininggasstreamispassedoverafinalbedofV2O5toproducea99.7%conversion.0.3%SO2

releasedisconsideredacceptable.Ø HighpressuresARENOTUSEDasitisnoteconomictousethemindustrially

3.Formationofoleum

Ø TheproducedSO3isreactedwithexistingsulfuricacidtoproduceoleum(athick,oilyliquid)Ø SO3(g)+H2SO4(l)àH2S2O7(l)Ø TheSO3isnotdirectlyreactedwithwater,asthereactionishighlyexothermicandwouldproducea

highlytoxicvapourofsulfuricacid,whichwouldbeincrediblydangeroustoplantworkers.

4.ProductionofH2SO4Ø H2S2O7(l)+H2O(l)à2H2SO4(l)Ø OleumisaddedtowatertoproducetwomolesofsulfuricacidØ Thisresultantacidis98%pure

EnvironmentalIssues

Ø SomeSO2inevitablyescapes,causingacidrainØ Exitinggasescanbepassedthrougha“scrubber”(containingthestronglyoxidisingCaro’sacid,H2SO5)

toconvertexcessSO2tosulfuricacidØ SpillageofacidsintransportandacidraindecreasespHofwaterwaysØ Thermalpollutioninterfereswithreproductivecyclesandmigratorycyclesofaquaticlifeand

increasestherateofweedgrowth.Italsolowerslevelsofdissolvedoxygenandothergases.


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• Describe,usingexamples,thereactionsofsulfuricacidactingasanoxidisingagentandasadehydratingagent• Performfirst-handinvestigationstoobservethereactionsofsulfuricacidactingasanoxidisingagentandasa

dehydratingagentØ DehydratingAgent

• C2H5OH(l)à(withconc. H;SOJ)C2H4(g)+H2O• CuSO4.5H2O(s)àCuSO4(s)+5H2O(l)(Saltgoesfromblueàwhite)• Esterification(H2SO4isusedasacatalyst)• Concentratedsulfuricacidwilldehydratesugar,leavingasolidcolumnofcarbon.Thesteam

producedinthereactioncausesthesolidcarbontoriseup• ThisexperimentmustbedoneinthefumecupboardasthesteamgeneratedwillcontainH2SO4,

whichishighlydangerous.C12H22O11(s)à12C(s)+11H2O(l)(H2SO4onarrow)

Ø OxidisingAgent

1)OxidisesIodide(colourless)toiodine(purple/brown)o Add2gofKIcrystalsintoatesttubeo AddafewdropsofH2SO4(l)totheKIinafumecupboardo Observethepurplegas(I2)o TestforSO2withfilterpapersoakedinacidifiedK2Cr2O7whichturnsfromorangetogreen(Cr3+)

§ Oxidation:2I-àI2+e-§ Reduction:4H++SO4

2-+2e-àSO2+2H2O(l)§ 4H++SO4

2-+2I-àI2+SO2+2H2O(l)• SO2(g)producedwillreduceacidifiedK2Cr2O7toCr3+whichisgreen• 2KI(s)+2H2SO4(l)àI2(g)+K2SO4(aq)+2H2O(l)2)Oxidisescoppermetal

o Sulfuristheoxidisingagentinconcentratedsulfuricacido Cu(s)+2H2SO4(l)àCuSO4(aq)+SO2(g)+2H2O(l)o S(s)+2H2SO4(l)→3SO2(g)+2H2O(l)o Hydrogenistheoxidisingagentindilutesulfuricacido Zn(s)+H2SO4(aq)àZnSO4(aq)+H2(g)

• Describeandexplaintheexothermicnatureofsulfuricacidionisation

H2SO4(l)+H2O(l)àH3O+(aq)+HSO4

-(aq) ΔH=-90kJ/mol

HSO4-(aq)+H2O(l) H3O(aq)+SO4

2-(aq) (35%ionisation)

Ø BondsBroken:O-HbondsinH2SO4Ø BondsFormed:CoordinatecovalentbondbetweenH2O&H+Ø ReasonsforExothermicNature

o FormationofthebondsthatmakeupH3O+releasevastamountsofenergy–morethanwhatisrequiredtobreakthebondthatheldthehydrogeninH2SO4(netlossofenergy)

o Energy:Form>Break(soenergyreleased,henceexothermic)

• IdentifyanddescribesafetyprecautionsthatmustbetakenwhenusinganddilutingconcentratedsulfuricacidØ SafetyIssues

• Ingestion=causeseriousburnsofmouth,etc.• Inhalation=corrosiveandhighlytoxic–causesevereirritationandburns• Skin=causesevereirritation,burns,charringofskin=flushwithwater,removeclothing• Eyes=causesevereburns,eyedamage=flushwithdirectsteamofwater• Ifspilledonbench=evacuate,isolateandneutralise(NaHCO3);weargogglesandclothingatall

times

Ø ToDiluteH2SO4• Slowlyaddasmallofamountofconc.H2SO4toalargeamountofH2Oàwatercanabsorband

dissipateproducedheat(duetolargeheatcapacity)(NEVERADDWATERTOACID,ALWAYSACIDTOWATER)


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• Ifwaterisaddedtosulfuricacid,theheatgeneratedwillturnthewaterintosteam,resultinginamistofsulfuricacidwhichisverydangerous

• Performwhilestirringandcoolinginfumecupboardwithprotectiveclothing/goggles• SpillscanbeneutralisedusingNaHCO3

Ø Precautionsforuse

• Weargloves• Wearsafetyglasses• Worknearasupplyofrunningwater• HaveasupplyforNa2CO3orNaHCO3nearby• Avoiddribblingtheaciddowntheoutsideofthebottleontothelabelwhenpouring• Useadriptray• Forregularuse,storeinglassbottlesnogreaterthan1litreinvolume

• Useavailableevidencetorelatethepropertiesofsulfuricacidtosafetyprecautionsnecessaryforitstransport

andstorageØ Conc.H2SO4=highmolarity(10M+etc.)=nearlyallmoleculesaremolecular(veryfewions)

• Doesnotattackstealoriron–ionscannotdissociatesodoesnotactasoxidant• H2SO4(l)isstoredandtransportedinsteelcontainersasitdoesnotreactwithsteelandthusthe

containerwillnotbreak• Ensurewateriskeptaway(fullyenclosedcontainers)–subsequentdilutioncancausedissociation

ofionsàcorrosionØ DiluteH2SO4=containsfreeH3O+ions=oxidisemetals

• Dilutesulfuricacid,however,hasH+,andwillreactwithsteeltoformironsulfate(FeSO4)• Cannotbestoredinsteelcontainers–useinertglassorplastictoavoidreactions• Smallcontainersstoredinplastictraysincaseofbreakage• Keepawayfromwood(exothermicdehydrationreaction)


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Section4Theindustrialproductionofsodiumhydroxiderequirestheuseofelectrolysis

• ExplainthedifferencebetweengalvaniccellsandelectrolyticcellsintermsofenergyrequirementsGalvanicCell ElectrolyticCell

Ø ChemicaltoElectricalEnergy(throughredoxandmetaldisplacementreactions)

Ø ProducesanelectriccurrentØ SpontaneousreactionØ Anodeis(-)Cathodeis(+)Ø E0ispositive

Ø ElectricaltoChemicalEnergy(throughredoxandmetaldisplacementreactions)

Ø RequiresinputofelectriccurrentØ Non-spontaneousreaction(forced)Ø Anodeis(+)Cathodeis(-)Ø E0isnegative

Ø GalvanicCellsusuallyconsistoftwohalfcellslinkedbyasaltbridgeandexternalcircuitØ ElectrolyticCellsusuallyconsistofonecontainerandasingleelectrolyte,withthecontainerseparatedhalfway

byamembranewhichonlyallowsionstopassthroughNOTE:VoltageofbatteryneedstobegreaterthanvoltageotherwiseproducedfromtheGalvaniccell(i.e.IfEMF=-1.1VthenVofbatteryneedstobe>1.1Vforelectrolyticcelltowork)

Ø Inbothcells,theanodeisoxidisedandthecathodeisreduced(THUSANOX/REDCATAPPLIESTOBOTH)Ø Electronflowisalwaysfromnegativetopositive

• Outlinethestepsintheindustrialproductionofsodiumhydroxidefromsodiumchloridesolutionanddescribethereactionintermsofnetionicandfullformulaeequations

• Distinguishbetweenthethreeelectrolysismethodsusedtoextractsodiumhydroxide:mercuryprocess,diaphragmprocessandmembraneprocessbydescribingeachprocessandanalysingthetechnicalandenvironmentaldifficultiesinvolvedineachprocessØ Electrolysis:Theprocesswherebyanelectricalcurrentisusedtobringaboutanon-spontaneouschemical

reaction(often,butnotalwaysdecomposition)Ø SodiumHydroxideisanextremelycommerciallysignificantalkali.Itisusedto:

o Makeproductsincludingplastics,soapsrayonandtextileso Revitalizingacidsinpetroleumrefiningo Removalofpainto Etchingaluminiumo Dehorningofcattleo Duringtwostepsofthepapermakingprocesso Usedinrelaxerstohelpstraightenhair

Ø Itisproducedbytheelectrolysisofsalt(brine)andwaterØ NaOHisclassifiedasastrongbaseasitundergoescompleteionisationØ ALL3INDUSTRIALPROCESSESBEGINWITHBRINEPURIFICATIONSTEPS.THISISDONEBYPRECIPITATION.


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o CalciumionsareremovedbyaddingsodiumcarbonateCa2+(aq)+CO3

2-(aq)àCaCO3(s)

o MagnesiumionsareremovedbyaddingsodiumhydroxideMg2+(aq)+2OH-

(aq)àMg(OH)2(s)o Ironionsareremovedbythesodiumcarbonateandsodiumhydroxide

Fe2+(aq)+CO32-(aq)àFeCO3(s)

Fe2+(aq)+2OH-(aq)àFe(OH)2(s)

o SulfateionsareremovedbyaddingcalciumchlorideSO4

2-(aq)+Ca2+(aq)àCaSO4(s)

TheMercuryCellØ Uptotheyear2000,thismethodwasusedinNSWtoproduceNaOH

CHEMISTRYØ Themercurycelliscomprisedoftwotanks,connectedbyflowingmercury,whichiscontinuouslypumped

throughaseriesofpipesØ Purifiedconcentratedbrinesolution(30%NaCl)ispumpedintothefirsttankofthecell,wherethe

chlorineanionsareoxidisedatatitaniumanodeformingchlorinegas–thisgasisthenremovedfromthemercurycellandstoredforotherpossibleuses

2Cl-(aq)àCl2(g)+2e-

Ø Thesodiumionsdissolveintheflowingstreamofmercury(thecathode)toformanamalgamNa+(aq)+e-àNa(s)

Ø Theflowingmercurythenflowsintothesecondtank,whichcontainspurifiedwaterØ ThesodiumintheamalgamreactswiththewaterandverypureNaOHandhydrogengasareformed

Na(Hg)+H2O(l)àNaOH(aq)+H2(g)+Hg(l)Ø ThehydrogengasisremovedfromthemercurycellandstoredforotherpossibleusesØ TheNaOHcanthenbetappedoff,andthemercurycanbepumpedbackintothefirsttank

OVERALL:2NaCl(aq)+2H2O(l)à2NaOH(aq)+Cl2(g)+H2(g)

CONSIDERATIONS

Ø Attheanode,chlorinegasisevolved;itisacorrosive,powerfuloxidisingagent.HenceanINERTanodeoftitaniumplatesisused.

Ø Mercuryisusedasthecathodebecause:o Itisaliquid,andcanbepumpedaroundasystemo Itreadilyformsalloys(amalgams)withmanymetals(e.g.sodium)o Whenusingamercurycathode,sodiumions,notwatermolecules,arepreferentiallyreduced,as

opposedtousingothercathodesØ Thetitaniumplatesareheldveryclosetothemercurysurfacetoallowforverylargecurrentflows;this

promoteselectrolysis(3to4voltsareused,butwithtensofthousandsofamperesofcurrent)Ø Therawmaterials(brineandwater)mustbepurifiedbeforeuseØ Thedepletedbrinemustbecontinuouslyreplacedwithfreshbrine

ENVIRONMENTALIMPACTSØ Althoughthesystemappearstobeclosed,smallmercurylossestotheenvironmentalareinevitable;100-

200gofmercuryisreleasedintotheenvironment(e.g.oceans)foreverytonneofNaOHproduced.Ø MercurycompoundscanbepassedontohumansbybiomagnificationØ Thisisofagreatconcern;mercuryisaheavy-metal,andaneurotoxinØ ThismethodisnotusedinNSWanymoreduetomercurytoxicityconcerns


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TheDiaphragmProcessCHEMISTRY

Ø ThecellconsistsofatitaniumanodeandsteelcathodeØ HassmallerelectricalrequirementscomparedtothemercurycellØ Purifiedsaturatedbrineisenteredintothecell,andthechlorineanionsareoxidisedattheanodetoform

chlorinegas.Thisgasisthensentoutofthecellandcollectedforotheruses.2Cl-(aq)àCl2(g)+2e-

Ø Thesodiumions,however,migratetothecathodebypassingthroughtheasbestosdiaphragmØ Purifiedwaterisenteredintothecellonthesideofthecathode,whereitisreducedtoformhydrogen

gasandhydroxideions.Thishydrogengasisalsosentoutofthecellandstoredforotheruses.2H2O(l)+2e-àH2(g)+2OH-

(aq)

Ø TheremainingNa+andOH-ionsinsolutionmakeuptheNaOH,whichisthensentoutofthecellOVERALL:2NaCl(aq)+2H2O(l)à2NaOH(aq)+Cl2(g)+H2(g)

CONSIDERATIONSØ Again,chlorinegasisevolvedattheanode,andhenceasuitablematerialmustbeused-mustbe

resistanttochemicalattackØ Chlorinemustbeseparatedfromthehydrogen,astheyreactvigorouslytoformcorrosiveHClgasØ Alargesystemofmanysmallcellsisemployed,insteadofonelargecellØ 3.5-5voltsused,withtensofthousandsofamperesofcurrent.Ø Theasbestosissupposedtoactasabarrierforthemovementofions,Ø allowingonlythemovementofNa+ionsintothesteelmesh,andpreventingthemovementofhydroxide

andchlorideions,however,someunwantedionmovementoccurs:o SmallamountsofCl−ionscrosstheasbestos,andreactwiththeNa+(formingsalt,NaCl,whichis

animpurityinthefinalproduct)andalsoreactwiththeOH−(formingthechloriteion,ClO−,astrongoxidant).

o SmallamountsofOH−ionsalsomovebackintothebrine,formingNaOHandClO−inthedepletedbrine.

Ø DuetothenatureofthediaphragmthefinalproductalwayscontainsNaCl,whichisonlypartiallyremovedbycrystallisation.

ENVIRONMENTALIMPACTS

Ø Asbestosfibresarequitedangerous,andinhalationofthesefibrescancausearangeoflungdiseases,suchasasbestosis

Ø Thedepletedbrinecannotbereleasedimmediatelybackintotheenvironment,duetothepresenceofsmallquantitiesofbasicNaOH,andoxidisingClO−ions,whichhavetoberemoved

Ø ClO-ionsharmaquaticorganisms,anddisruptthefoodchain

TheMembraneProcessCHEMISTRY

Ø ThecellconsistsofatitaniumanodeandsteelcathodeØ Asinglecellisdividedintotwohalvesbyanion-exchangepolymermembranemadeof

polytetrafluoroethylene(Teflon).Ø Thismembraneisselectivelypermeable,andallowsthediffusionofwaterandsodiumionsONLY.

Chlorideandhydroxideionscannotpass.(UNLIKEINTHEDIAPHRAGMPROCESS)Ø Inthefirsthalf,brineispumpedin,andwaterinthesecondhalf.


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Ø Onthetitaniumanode,chlorineisproduced,andonthenickelcathode,hydrogenandhydroxideionsareproduced.

o 2Cl-(aq)àCl2(g)+2e-o 2H2O(l)+2e-àH2(g)+2OH-

(aq)o Overallequationalsoidenticaltothatofthediaphragmprocess

Ø Thesodiumionspassthroughthemembrane,andcombinewiththehydroxideions,formingverypureNaOH,whichiscontinuouslyremoved.

Ø Thestructureofthecellisidenticaltothatofthediaphragmprocess,onlythattheasbestosdiaphragmisreplacedwiththepolytetrafluoroethylenemembrane.CONSIDERATIONS

Ø Thiscellsolvestheproblemsofboththemercuryanddiaphragmcellso Therearenotoxicmaterialsused,suchasmercuryorasbestos;averyinertpolymerisusedas

themembrane.o VerypureNaOHisformed,aswiththemercurycell,asthereisnocontaminationoftheproduct

withchlorideions,andthedepletedbrineisjustNaClsolution.o Titaniumisusedasanodeasitwithstandschlorineattack.

Ø Thepolymerhasmanyusefulproperties,suchasitsselectivepermeability,aswellasitsabilitytoresistchemicalattackinastronglybasicsolution

Ø Justaswiththediaphragmcell,alargesystemofmanysmallcellsisemployed,insteadofonelargecello 3.5-5voltsused,withtensofthousandsofamperesofcurrent

ENVIRONMENTALIMPACTSØ Becauseofthenatureofthemembrane,andtheinertelectrodesused,thereareveryfewenvironmental

issuesassociatedwiththiscellØ IssuesincludetheleakageofchlorinegasandNaOHintotheenvironmentØ Excessbrinemustnotbedepositedintowaterways,asthiswillincreasethesalinityandupsetthenatural

balanceØ Ascomparedtothetwoothercells,thiscellproducesveryhighqualityNaOHwithalmostno

environmentalorhealthissuesandconcerns

NON-SPECIFICTECHNICALITIESThelocationoftheplantisatechnicalconsiderationthatmustbeinaccordancewiththeavailabilityofthefollowing:

• Cheapelectricity(asthisisTHEmajorcost)• Theremustbecheapbrineaswellasfreshwatersources• Alocalworkforcewillingtoworkatsuitableexpenditure• Itmustbebuiltawayfromurbanandresidentialareas,duetothelargeamountsofnoiseandheat

thattheplantsemit• Suitablewastedisposalmustbeavailable


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• Identify,planandperformafirsthandinvestigationtoidentifytheproductsoftheelectrolysisofanaqueoussolutionofsodiumchlorideØ Aim:ToinvestigatethechemistryinvolvedinelectrolysingdifferentaqueoussolutionsofsodiumchlorideØ Safety:Wearsafetyglassesandprotectiveclothing.Makesurepowersourceisturnedoffwhenconnecting

anddisconnectingelectrodes.Chlorinegasispoisonoussoworkinafumecupboardandavoidbreathingthevapour.

Ø Equipmentrequired:• HofmannVoltameter• RetortStandandClamp• DCPowerSource(0-12V)• 2Electricalleadswithalligatorclips

• GraphiteORTitaniumelectrodes• 50mlsaturatedsodiumchloridesolution• 5oml0.1mol/Lsodiumchloridesolution• Universalindicator

Ø Procedure(A–Electrolysisofsaturatedsodiumchloridesolutionwithinertelectrodes)1. FilltheHofmannVoltameterwithsodiumchloridesolution.2. Addafewdropsphenolphthaleinindicatortothevoltameter.3. Connecttheelectrodes(graphiteORtitanium)totheDCpowersupplyusingtheelectricalleads

provided.Ensuretheelectrodesareabouthalfcoveredwithsolution.4. Setthepowersupplyto6-8Vandswitchonthepower.Youmayneedtoadjustthepoweroutput.

Electrolysethesolutionfor2-3minutes.5. Observeandrecordanychanges,suchascolouroftheindicatororevolutionofgasateach

electrode.6. Switchoffthepowersupply.7. Holdastripofmoistredlitmuspaperovertheanodecompartmentandopenthevalve.(Thepaper

shouldbebleachedwhitebythechlorinegas)8. Collectthegasatthecathodeinatesttubeandperformthepoptest.(Thegasishydrogen)9. Determinetheanionproducedatthecathodeofthevoltameter(phenolphthaleinwillbepurpledue

totheproductionofhydroxideions).10. Recordallobservationsinaresultstable.

Ø Procedure(B–Electrolysisof0.1mol/Lsodiumchloridesolution)1. Repeatsteps1-7asforpartAusingthedilutesolutionofsodiumchloride

(Insteadoftestingforchlorinegas,testforoxygengasbycollectinginatesttubeandcheckingifthegasisabletorelightaglowingsplint)

Ø Results Observations

Anode CathodePartA ChlorineGas

(BubblingatElectrode)(BleachesmoistredLitmusPaper)

HydrogenGas(BasicpH)(BubblingatElectrode)(PositivetoPopTest)

PartB OxygenGas(AcidicpH)(BubblingatElectrode)

(Reignitesanextinguishedsplint)

HydrogenGas(BasicpH)(BubblingatElectrode)(PositivetoPopTest)


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• AnalyseinformationfromsecondarysourcestopredictandexplainthedifferentproductsoftheelectrolysisofaqueousandmoltensodiumchlorideØ DiluteNaCl(1mol/L)–Na,Cl,H2O

o ANODE:2H2O(l)àO2(g)+4H+(aq)+4e- EOX=-1.23V

o CATHODE:2H2O(l)+2e-àH2(g)+2OH-(aq) ERED=0.83V

o ECELL=-2.06V(NONSPONTANEOUS)v Gasbubblesattheanodewillrekindleaglowingsplitv Gasbubblesatthecathodewilltestpositivetothe‘poptest’v Phenolphthaleinwillturnpinkatthecathodeduetothehydroxideproduced

Ø ConcentratedNaCl(5mol/L)–Na,Cl,H2Oo ANODE:2Cl-(aq)àCl2(g)+2e-o CATHODE:2H2O(l)+2e-àH2(g)+2OH-

(aq)o As[Cl-]ismorethan1mol/Litwillgetoxidisedinsteadofwater.Thedifferenceinvoltageisapprox.

0.1Vo Na+willnotgetreducedatthecathodeasthedifferenceinvoltageisapprox.2V,morethanthatof

waterv Chlorinegasattheanodev Moistredlitmuspaperwillbebleachedwhiteaschorinegasisableachingagentv Hydrogengasandhydroxideatthecathode–sametestsasforthediluteNaCl

Ø MoltenNaCl–Na,Clo ANODE:2Cl-(l)àCl2(g)+2e-o Cathode:Na+(l)+e-àNa(l)o SilveryglobuleswhenaddedtowaterwillreactvigorouslyproducinghydrogengasandNaOH


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Section5Saponificationisanimportantorganicindustrialprocess

• DescribesaponificationastheconversioninbasicsolutionoffatsandoilstoglycerolandsaltsoffattyacidsØ Saponificationistheconversionoffatsandoilstosoapandglycerol

byreactingthefatsandoilswithconcentratedNaOHorKOH(theconversion,inbasicsolution,offatsandoilsintoglycerolandthesaltsoffattyacids)

Ø FatsandoilsaretriglyceridesØ Thenumberofhydrogenatomscanchangeasthelongcarbonchain

canhavedoublebonds(mainlyinoils)orcanbesaturated(mainlyinfats)

Ø Soapisthesodiumsaltoffattyacids

E.G.GlycerylTripalmitate+SodiumHydroxideàGlycerol+SodiumPalmitate

Ø Thesodiumhydroxide(NaOH)splitsthetriglyceride(hydrolysis)alongtheesterbond(–COOC–)Ø The3hydroxylgroups(OH-)attachtotheglyceryl,formingglycerolØ Thefattyacids(carboxylateions)reactwiththeNa+ions,formingthe3“saltsoffattyacids”(inthiscase

sodiumpalmitate)

• Glycerolo Glycerolisatri-alcoholcompoundderivedfrompropane,itcontainsanalcohol

group(ahydroxyl)oneverycarbono UsingIUPACnomenclature,anothernameforglycerolispropane-1,2,3-triolo Widelyusedinthefoodindustryasasweetenerandhumectant(reducesthe

lossofmoisturebyforminghydrogenbondswithwater)andinpharmaceuticalformulations

o UsedinIceCream,skinlotions,mouthwashes,coughmedicines,etc.

• FattyAcidso Fattyacidsarelongcarboxylicacidsthatoccurinfatsandoils.o Therearemanytypesoffattyacids,whichvaryinthenumberofcarbons(12-18)aswellasinthe

degreeofsaturation(doublebonds).o LauricAcid(12-C)

§ CH3-(CH2)10-COOHo LinoleicAcid(18-C)

§ CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-(CH2)7-COOH

• FatsandOilso OrganiccompoundsknownasTriglycerides

§ Fatsaresolidandoilsareliquidatroomtemperature.o Atriglycerideisacompoundinwhichall3hydroxylgroupsofaglycerolmoleculehavebeen

ESTERIFIEDwithcarboxylgroupsfromthreefattyacidchains,waterisaby-product.o Threeesterbondsareformed;triglyceridesaretri-esters.o Thenaturalformationoffatsandoilsisanesterificationreaction.


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• Saponification

o Reversaloftheprocessthatformsfatsandoils.o Thereactionbetweenanesterandhydroxideiontoformanalcoholandacarboxylateanion.o Hydrolysisofanesterunderalkalineconditions.o Conversion,inbasicsolution,offatsandoilsintoglycerolandthesaltsoffattyacids.o Saltsoffattyacids,suchassodiumstearate,areSOAPS.o Saponificationisthechemicalprocessofproducingsoaps.

o Sodiumhydroxide(NaOH)splitsthetriglyceride(hydrolysis)alongtheesterbond(-COOC-)

§ The3hydroxylgroups(OH-)attachtotheglycerylformingglycerol.o Thefattyacids(carboxylateions)reactwiththeNa+ions,formingthe3saltsoffattyacids–

sodiumstearate.

• Describetheconditionsunderwhichsaponificationcanbeperformedintheschoollaboratoryandcomparethesewithindustrialpreparationofsoap

• Performafirst-handinvestigationtocarryoutsaponificationandtesttheproductØ Method

1. Mix20mLofoliveoilwith5mLof4mol/LNaOHinabeaker(withboilingchips)2. Gentlyboilonahotplatewithconstantstirring3. AddmoreNaOHuntilsolidparticlesseparate4. Coolandadd10mlofsaturatedNaClsolution(‘saltingout’,asNaClismoresolubleinwaterthan

thesodiumsaltoffattyacids,thesoapwillprecipitate)5. Thesoapisfilteredandwashedwithwatertoremovethesurfacealkali(whichhiscaustic)6. Perfumeandcolourmaybeadded,andthesoapismouldedintoshape

Ø RiskAssessmentIdentify Assess Control

ConcentratedNaOH Caustic–willdissolveproteins Wearsafetyglasses,gloves,alongsleevedlabcoatandenclosedshoes

HotOil Causesburnstotheskinwhenhot+Flammable

UseofahotplateasopposedtoaBunsenflameConstantstirringofmixturepreventsthespittingofhotoil

Ø Comparisonof‘SchoolMethod’with‘IndustrialMethod’School Industry

Usedvegetableoil Choppedupanimalfat4mol/LNaOH 30%w/vNaOHBoil HeatuntilallfatisdissolvedMixwithNaCl NearlysaturatedbrineSoapisfiltered ScoopedoutfromthetopThefiltrateisdiscarded Glycerolseparatedfromtheaqueouslayers.


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• AccountforthecleaningactionofsoapbydescribingitsstructureØ Whenaddedtowater,thesodiumsaltofafattyacid

dissociatestoproduceasodiumcationandanegativelychargedfattyacidanion

Ø Theheadofthesoapion(COO-)ispolar,andthushydrophilic(solubleinwater)

Ø Thetailofthesoapisnonpolar(hydrocarbonchain)andisthusinsolubleinwater(hydrophobic),butsolubleinfatsandoils

Ø Asurfactant(surfaceactingagent)isachemical“wetting-agent”thatlowerstheinterfacialtensionbetweentwoliquids,andhence,allowsthemtomix

Ø SOAPisasurfactant;itallowspolarwaterandnon-polargrease/dirttomixØ Becauseofthis,thesoapionwillformmicellesinwater,wherethepolarheadformshydrogenbonds

withthewater,andthetaildissolvesinoilandgreasedropletsduetoweakdispersionforcesØ Throughtheprocessofagitation,themicellesbecomesuspendedinthewater,forminganemulsionØ Thegreaseandoilcannowbewashedaway,leavingacleansurface

Ø Soapcleansandremovesgrease/dirtfromobjectsbythefollowingsteps:

1. Adirtyobjectisplacedinsoapywater.2. Thesoapimmediatelybeginstoattachtothegrease(thehydrophobictailspenetratethegrease

BUTthehydrophilicheadremainsinthewater)3. Thegreaseisliftedofftheobjectasthesoapsurroundsthegrease.4. Thegreaseiscompletelyliftedofftheobject,andissurroundedbysoap.

Ø Thegreasemoleculeiscompletelyencasedwithinasheathofsoapmoleculeswiththeirhydrophilicheadsincontactwithwater,whilethehydrophobictailscontainthegreasemolecule;thissheathallowsittodissolveinwater.

Ø Asthemixtureisagitated,moregreaseisliftedofthesurfaceofthedirtyobject,andmoregrease/soapparticlesareformed.

Ø Thegrease/soapparticlesarenegativelycharged(duetothenegativeheadofthesoap),andhencetheyrepeleachother,preventingthegreasefromclumpingbacktogether.

Ø Thesewatersolubleparticlesarethensimplywashedoffwithwater:

• Explainthatsoap,waterandoiltogetherformanemulsionwiththesoapactingasanemulsifierØ Anemulsionisastablemixtureof2immiscibleliquids,withtinydropletsofoneliquidevenlydispersed

throughouttheother.Ø Normally,mixturesof2immiscibleliquidsrapidlyseparate(suchasoilandwater);emulsionsare

stabilisedbytheactionofEMULSIFIERS:o Emulsifiersarethesameassurfactants.o Theyreducetheinterfacialtensiontoallowimmiscibleliquidstomix

Ø Intheexampleofawater/oilemulsion,theemulsifierusedissoap;henceasoapyoil/watermixtureconsistsofoilparticlesevenlydispersedthroughoutthewater.

Ø Inthiscase,thereismorewaterthanoil,andhencetheoilisdispersedthroughoutthewater;iftherewasmoreoilthanwater,thewaterwouldbedispersedthroughouttheoil,asisthecasewithbutter

Ø Thenon-polartailsofsoapmoleculesgatheraroundoildroplets,sothatthenegativelychargepolarendsfaceoutwards.

Ø Thiscreatesanegativechargeonthedropletofoilwhichrepelsothernegativelychargessoapandoildroplets,preventingtheformationoflargeclumpsofoil.


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Ø Thisalsoallowswatertointeractwiththeoildroplets.Thusoildropletsaredistributedthroughthewater.

• Distinguishbetweensoapsandsyntheticdetergentsintermsofthestructureofthemolecule,chemical

compositionandeffectinhardwater• Distinguishbetweenanionic,cationicandnon-ionicsyntheticdetergentsintermsofchemicalcompositionand

usesTypeofSurfactant Structure Chemical

CompositionEffectinHardWater

Soapuses Howtheywork

Soap(SodiumStereate)NaCH3(CH2)16COO

C,H,O,Na+ Ca2+/Mg2+formsascumwithfattyacid–doesnotwork.

PersonalHygiene Formsmicellesinwater.Oildissolvesinlonghydrophobictailandanionicheaddissolvesinwater.

Anionic–AlkylBenzeneSulfanoates(3oxygens)

C,H,O,S,Na+,K+ DoesnotprecipitatewithCa2+,Mg2+butdoesnotworkwellinhardwater.

Laundryliquidsandshampoos.Generatelargeamountsoffoam.

Similartosoap,anionicheaddissolvesinwatermakinghydrogenbondsandion-dipoleinteractives.

AlkylSulfanoates(4oxygens)

Non-ionicEthoxylatesmolecules(Noions)

C,H,O WorkswellasMg2+,Ca2+donotreact

Usedinpaintsandfront–loadingwashingmachines.Cosmeticsandpesticides.Wherefoamislessdesirable.

Ethoxygroupsformhydrogenbondswithsurroundingwatermolecules.

Cationic

C,H,N,Cl-

Quartenaryammoniumderivativeswhere3Hhavebeenreplacedwithmethylgroupsandoneisreplacedbyhydrocarbonchain.

WorkswellasCa2+,Mg2+donotreactwithcation.

Fabricsoftenersandhairconditioners.Positiveheadsattachtothenegativehairscales,leavingsmoothfeelandshinypart.

Negativechargeonwetclothesandhairattractthepositivehead.Thefabricorhairiscoatedwithhydrocarbonchainàreducesstatic.

• Gather,processandpresentinformationfromsecondarysourcestoidentifyarangeoffatsandoilsusedforsoap-

makingØ Tallow:Processedanimal-fats(usuallywaste).Itproducescommonsoap.Ø CoconutOil:Pressedoutofdriedcoconuts(copra);itisarelativelypureoil.Thisproducesahardsoap

thatlathersverywell.Ø SheaButter:Thefatderivedfromthefruit(ornut)ortheSheatree.Itproducesasoftsoapthatisvery

moisturisingandgentleonskin.Ø Animalfatsuchascattleandsheep.Ø Vegetableoilssuchascoconut,olive,sunflower.Ø Vegetablefatssuchascocoabutter.

• Performafirst-handinvestigationtogatherinformationanddescribethepropertiesofanamedemulsionand

relatethesepropertiestoitsusesØ NaturalEmulsifiers(surfactants)

o Caseineinmilkkeepsoildropletsdispersedinwater.o Lechitinfromeggyolkkeepsoil/wateremulsioninmayonnaise.

Ø NamedEmulsion:Buttero Smallamountofwaterisdispersedinoil.o Duetothefatinthebutteritcanbespreadonthebreadwithoutthebreadabsorbingthewater.o Duetothewaterinthebutter,watersolublesubstancessuchassaltandfooddyecanbemixed.


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Ø Mayonnaiseo Mayonnaiseisanemulsionofvegetableoilandeggyolks,withtheemulsifierbeingthelecithin

foundnaturallyintheeggyolk.o Otheradditionsmaybemadeforflavour,suchasvinegar,mustardofsalt,butthebasic

compositionofmayonnaiseisoilandeggyolks.o Mayonnaiseismadebyslowlyaddingoiltoaneggyolk,whilewhiskingvigorouslytodispersethe

oil;thelecithinstabilisesthemixture.Ø PropertiesinRelationtoUses:

o MayonnaiseisaverySTABLEemulsion,duetothestrongemulsifyingpropertiesoflecithin.Itdoesnotseparateintoitscomponentliquidsevenwhenstoredforlongperiodsoftime.

o Thispropertyisusefulasitisafoodproduct;itneedstostayinanediblecondition,instorage,forrelativelylongperiodsoftime.

o Mayonnaisealsohasthepropertyofhavingacreamy‘mouth-feel’,andnotfeelingoily.Mostpeoplefindthesensationofeatingpureoilunpleasant,butfindthecreamytasteofmayonnaiseenjoyable.However,mayonnaiseisactuallyonaverage75%oil.Thepropertyoftheemulsionashavingacreamytextureaddstoitsuseasafood.

• Performafirst-handinvestigationtodemonstratetheeffectofsoapasanemulsifierMethod

1. Add2mLofwaterand2mLofoilintotwotesttubes.2. Add2gofsoapintoonetesttube.3. Mixboththetesttubesuntiltheoilisdispersedinwatergivinga

homogenoussolution.4. Leavefor10minutesundisturbedandobserve.

ResultsØ Thesolutionwithoutthesoapseparatedintooilandwater.The

solutionwiththesoapstaysdispersed.

• Solveproblemsanduseavailableevidencetodiscuss,usingexamples,theenvironmentalimpactsoftheuseofsoapsanddetergents

Ø Biodegradability:o Soaphasverylittleenvironmentalimpactbecauseitisveryeasilybrokendownintocarbon

dioxideandwaterduetotheactionofbacteria.o Therearetwotypesofanionicdetergents:detergentswithbranchedchains,anddetergentswith

unbranched(linear)chains:§ Branched-chainanionicdetergentswerethefirstdetergentsformed.Theywerenot

biodegradable,andledtoconsiderableenvironmentalproblems:• Detergentbuiltupinwaterways,andriversanddamswereconstantlycovered

inlayersoffoam• Itwasaestheticallyandenvironmentallyunwanted• Thefoamreducedsunlightenteringthewater,affectingthephotosynthesisof

waterplants.Thisledtoadropindissolvedoxygenlevels.§ Thelineardetergentswerethencreated;thesearemuchmorebiodegradablethanthe

brancheddetergentsandsolvedthefoamproblem.


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Ø ExcessLevelsofPhosphates:o Soapsdonotcontainanyphosphateso AnionicdetergentsareaffectedslightlybythepresenceofMg2+andCa2+ionsinhard-watero Substancescalled‘builders’areaddedtodetergentstoincreasetheirefficiencyo Builders(suchassodiumtripolyphosphate:Na5P3O10)reactwiththeionsinhard-water,softening

thewater.Buildersalsoincreasethealkalinityofthewater,whichincreasesthedetergentscleaningpower.

o However,theincreasinglevelofphosphatesinwaterwaysasaresultofphosphatebuildersisamajorenvironmentalproblem.

§ Excessphosphatesinwaterwaysleadtoeutrophication,whichsubsequentlyleadtoalgalblooms

§ Asaresultofthealgalbloom,thebiologicaloxygendemandofthewaterwaywillincrease,leadingtoasubsequentdecreaseindissolvedoxygen

§ Thisdecreaseindissolvedoxygencausesstresstoaquaticlife,asthereisnolongersufficientoxygeninthewatertoadequatelysupporttheseorganisms

§ Thealgaecoverthesurfaceofthewaterway,preventinglightfromenteringintothewaterway.Thispreventsaquaticplantsfromphotosynthesising,causingfurtherdamagetoorganismswithinthewaterway.

o Thiscausesseveredegradationofwaterquality,thepromotionofanaerobicconditionsandthedisturbanceofanaturalecosystem

Ø BiocidalEffectsofCationicDetergentso Cationicdetergentshavemildbiocidalproperties,astheydisruptthecellularprocessesin

bacterialcellso Thus,theirpresenceinwastewaterandseweragecancausethebacteriawhichbreaksdown

wastetobekilled.o Thisoccursathigherconcentrationsonly;lowerconcentrationsofcationicdetergentsdon’t

harmthebacteriawhichbreakthemdown.o Athigherconcentrations,thesebiocidalpropertiescanstartharminglargerorganismsin

waterways.Ø Issuesrelatingtonon-ionicdetergents

o Whendisposedofintowaterways,transformedtoalkylphenolsthroughbiologicaldegradation.Alkylphenolsaretoxicandhavehormone-likeeffectsonmarineandfreshwaterlife.


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Section6TheSolvayprocesshasbeeninusesincethe1860s

• IdentifytherawmaterialsusedintheSolvayprocessandnametheproductsØ Rawmaterialsaresodiumchloride(NaCl-brine),ammonia(NH3)andcalciumcarbonate(CaCO3-limestone)Ø Productsaresodiumcarbonate(Na2CO3)andcalciumchloride(CaCl2-waste)

• Describetheusesofsodiumcarbonate

1. Glassmaking:Na2CO3andsandareusedtomakesodaglass,whichcanbeeasilymoulded2. MakingofsoapsanddetergentsasareplacementforNaOH3. Commonbasefortheneutralisationofacidicspills4. Usedinthesofteningofhardwater,removescalciumandmagnesiumfromwaterascarbonates5. Usedinthemanufacturingofpapertoseparatecellulosefromlignin6. UsedinthemanufactureofNaHCO3bakingsoda7. Usedtoremovesulfurdioxidefromwastegassesinpowerstations

• Identify,givenaflowchart,thesequenceofstepsusedintheSolvayprocessanddescribethechemistryinvolved

inbrinepurification,hydrogencarbonateformation,formationofsodiumcarbonateandammoniarecovery

OVERALLSOLVAYEQUATION:2NaCl(aq)+CaCO3(s)àNa2CO3(s)+CaCl2(aq)

ReactionsSummary:• LimeKiln:CaCO3(s)à(heat)CaO(s)+CO2(g)• Carbonator:CO2(g)+NaCl(aq)+NH3(aq)+H2O(l)àNaHCO3(s)+NH4Cl(aq)• Converter:2NaHCO3(s)à(heatat300°C)Na2CO3(s)+H2O(g)+CO2(g)• Slaker:CaO(s)+H2O(l)àCa(OH)2(aq)• AmmoniaRecoveryUnit:Ca(OH)2(aq)+2NH4Cl(aq)àCaCl2(aq)+2NH3(g)+2H2O(l)

Ø Stages1.BrinePurification(SAMEASPURIFICATIONUSEDINPRODUCTIONOFNaOH)

• Brineisobtainedfromsaltwater(underground),rocksaltdepositsandfromseawater• Thesesourcesoftencontainimpurities,suchasCa,Mg,Feandsmallamountsofheavymetalso Na2CO3isusedtoprecipitateoutcalciumo NaOHisusedtoprecipitateoutmagnesium,ironandtheotherheavymetalso Alltheprecipitatedmetalscanthenbefilteredfromthebrine

Ca2+(aq)+CO32-(aq)àCaCO3(s)

Mg2+(aq)+2OH-(aq)àMg(OH)2(s)

Fe3+(aq)+3OH-(aq)àFe(OH)3(s)

2.DecompositionofCaCO3

• CaCO3isneededintheSolvayprocessinordertoproduceCO2(g)forthecarbonatorCaCO3(s)à(heat)CaO(s)+CO2(g)


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3.HydrogenCarbonateFormationCO2(g)+H2O(l) H2CO3(aq)

H2CO3(aq)+NH3(aq) NH4+(aq)+HCO3

-(aq)

HCO3-(aq)+Na+(aq) NaHCO3(s)

OVERALL:CO2(g)+NaCl(aq)+NH3(aq)+H2O(l)à(at0°C)NaHCO3(s)+NH4Cl(aq)• Whenthisreactionisperformedatlowertemperatures(0°C)thenormallysolubleNaHCO3instead

formsasolidwhichcanbefilteredfromNH4Cl(aq)• NH3willpivottheformationofHCO3

-(asH2CO3isaweakacidandwithalowdegreeofionisationwithoutammonia)

H2CO3(aq)+H2O(l) HCO3-(aq)+H3O+

(aq)(Thisequilibriumliesheavilytowardtheleft,henceusingammoniaisadvantageous)

4.FormationofSodiumCarbonate

• ThesolidNaHCO3isthenfilteredoffandheadedinaconverter2NaHCO3(s)à(heatat300°C)Na2CO3(s)+H2O(g)+CO2(g)

5.AmmoniaRecovery

• Calciumhydroxideisproducedintheslaker,wherecalciumoxidefromthelimekilnisreactedwithwater

• Thiscalciumhydroxideisreactedwithammoniumchloridetoproduceammoniagas,whichisthensenttothecarbonatorwhereitcantakepartinthereactiononceagain

CaCO3(s)à(heat)CaO(s)+CO2(g)

CaO(s)+H2O(l)àCa(OH)2(aq)Ca(OH)2(aq)+2NH4Cl(aq)àCaCl2(aq)+2NH3(g)+2H2O(l)

• DiscussenvironmentalissuesassociatedwiththeSolvayprocessandexplainhowtheseissuesareaddressed

Ø DisposalofwasteCaCl2• Ifcalciumchlorideisdisposeddirectlyintotheocean,itwillincrease[Cl-]andTDS,displacingdissolved

oxygenandcarbondioxidegas(hencewillcausestresstoaquaticlife)• Ifcalciumchlorideisburiedunderground,itmaybeleachedintosurroundingsoil,toxifyingit• Solutions:

o Reusethecalciumchlorideasadryingagentoradditiveforconcreteandbrickso Dilutethecalciumchloridebeforeitisdischargedintotheoceano Evaporatethecalciumchloridetodrynessandburyinspecialisedburialsites

Ø AmmoniaLoss• Ammoniaisatoxicairpollutant• Solutions:

o Carefullymonitorandmanageammoniaconcentrationsintheair.Usespecialisedequipmenttomonitorammonialeakage.

Ø ThermalPollution• Wasteheatcancausethermalpollution,whichresultsinreducedamountsofcarbondioxideandoxygenin

waterways,causingstresstoaquaticlifeanddisruptingthemigratorycyclesoffish• Solutions:

o Ifnearocean,dilutewithcoldwateranddischarge.Ifinland,usecoolingpools.Ø Mining

• Miningofbrineandcalciumcarbonatecancauseearthsubsidence,destructionofhabitatsandthereleaseoftoxicfumes,particulatesanddustintotheatmosphere(causingpollutionandrespiratorydifficulties)

• Solutions:o Backfillingminedareas,usingdustscrubberstoreducetheamountofairpollutantsreleased


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• Performafirst-handinvestigationtoassessriskfactorsandthencarryoutachemicalstepinvolvedintheSolvayprocess,identifyinganydifficultiesassociatedwiththelaboratorymodellingofthestepØ Thedecompositionofsodiumhydrogencarbonate(NaHCO3)that

takesplaceintheconverterØ Results

• Carbondioxidegasproducedcauseslimewatertobubbleandturnmilky

Ø Difficultiesincarryingouttheexperiment• Iftheflameisremoved,thelimewateris‘suckedback’through

thedeliverytubecreatingbothsteamandpressureàCausesglassequipmenttocrackorbreak.Thickpyrexglasstesttubesarethereforeused,andlimewaterisremovedbeforeremovingtheBunsenburner.

• Processinformationtosolveproblemsandquantitativelyanalysetherelativequantitiesofreactantsandproducts

ineachstepoftheprocess(mole,concentration,volume,massyieldproblems,self-explanatory)

• UseavailableevidencetodeterminethecriteriausedtolocateachemicalindustryusingtheSolvayprocessasanexampleØ AvailabilityofRawMaterials

• Theplantmustbelocatednearaminingarea(limestone)ornearthesea(brine).Ideally,theplantshouldalsobelocatedneartransportlinestoallowforeffectiveimportandexportlogistics.

Ø AvailabilityofEnergy&Labour• Theplantshouldbelocatednearapowerdistributionstation,asitischeapertouseanexistingpower

distribution• Theplantshouldbelocatednearapopulationcentretoallowforeasytransportforworkersand

employeesØ LocationofMarkets

• Ideally,theplantshouldbelocatednearapopulationandinproximitytootherindustries(e.g.glassfactory)

• TheplantcouldalsobelocatedneartheseatoallowforseatradeØ DisposalofWaste

• Forthedisposalofcalciumchloride,theplantshouldbelocatednearthesea• Topreventextensivethermalpollution,theplantshouldalsobelocatednearthesea

Ø AmmoniaLeakage• Theplantisbestlocatedawayfrompopulationsduetothetoxicityofammonia

Ø OVERALLTHEPLANTSHOULDBELOCATED:o Outsidethepopulationcentre,butnotinaremoteareaeither(ontheoutskirts)o Neartheseaforasupplyofbrine,awaytodischargewasteandtoavoidthermalpollutiono Neartransportlinesforeffectiveimportandexportlogistics

industrial chemistry notes - acehsc · industrial chemistry notes – rohan barar 2016 1 industrial...

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