Chemistryinyourcupboard:CillitBang
Introduction
Dirt and stains can be categorised according to their constituents into water‐soluble,
particulate, fats/oils, proteins/carbohydrates and oxidisable components, although the
majority of cases will contain a mixture of these. There is no one product that can
removealldirt;theCillitBangbrandcoversawiderangeofcleanerswhichuseavariety
ofchemicalmethodstoremovedirtandstains.
Linkstothecurriculum
This section contains information relevant to the following areas of your chemistry
curriculum:
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

Group1elements
Bonding
Weakacids
CILLITBANG
Notalldirtisthesame,soremovingdifferenttypesofdirtwillrequirearangeof
differenttypesofcleaners.TheCillitBangfamilyofcleanersusesavarietyofchemical
methodstoremovedirtandstains.Table1showsexamplesofanumberoftypesofdirt
andstains.
Water‐soluble Particulate
Fats/oils
Proteins/
Carbohydrates
Oxidizable
Inorganicsalts
Metaloxides Vegetableoil
Blood
Fruits
Sugar
Clays
Animalfat
Egg
Vegetables
Urea
Carbon
Humansebum Milk
Waxes
Starches
Table1:Typesofdirtandstains
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Wine
Coffee/Tea
Sometypesofcleaningagentsarelistedbelow.



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bleaches
detergents(surfactants)
solvents
acids
CillitBangisabrandratherthanasingleproduct.Itincludesarangeofcleanersfor
differenttypesofdirt.Thebrandismarketedthroughouttheworldandthereare
differentformulationsfordifferenttypesofcleaning,Figure1.Theproductsalsodiffer
indifferentcountriestofitpeople’scleaninghabitsandlocalregulationsastowhat
componentscanbeincluded.
Figure1:PartoftheCillitBangrangeofproducts
ItwouldbeimpossibletocovereverymemberoftheCillitBangfamilyheresowewill
lookatarepresentativerangeofthedifferenttypes.
TheCillitBangrangecanbebrokendownintothreemaintypesofproduct
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

‘LimeandGrime’rangeofcleanersbasedonacids
Toiletcleaners–basedonbleaches
Degreasers–alkaline,basedondetergentsandsolvents
Acid–basedcleaners
Limescaleisadepositthatmayformaroundtaps(particularlyhottaps).
Question1
Givetworeasonswhythecalciumcarbonatedepositformsmorereadilyonthe
hottapofasinkratherthanthecoldone.
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Figure2:Formationoflimescaledepositaroundleakingvalves
Itiscomposedofcalciumcarbonate,whichisinsolubleinwater.Itoriginatesfrom
dissolvedcalciumhydrogencarbonate,whichisoneofthecomponentsofhardwater
(seeCalgon).
Thehydrogencarbonateisformedwhenrain,naturallyacidicduetodissolvedcarbon
dioxide,dissolvescalciumcarbonate(limestone)asitseepsthroughthegroundbefore
beingcollectedinareservoir,forexample.
CaCO3(s)+H2O(l)+CO2(g) Ca(HCO3)2(aq)ΔH=‐ve
Whendropsofhardwaterareleftonasurface,thewaterevaporatesandtheabove
equilibriummovestothelefttoleaveinsolublecalciumcarbonate‐awhitishdeposit.
Calciumcarbonateisvirtuallyinsolubleinwaterbutitissolubleinacids(aswehave
seenwhenlimestonerockdissolvesinacidicrain).Strictly,thecalciumcarbonateisnot
dissolving,itisreactingwiththeacid.So,anacid‐basedproductwillbeeffectivein
dissolvinglimescale.
CillitBangLimeandGrime(1of2)
Thisfamilyofcleanersisbasedaroundaformulationcontainingacidsincludingthe
following



Sulfamicacid(HOSO2NH2)pKa=0.99
Formicacid(HCOOH)pKa=3.8
Phosphoricacid(H3PO4)pKa1=2.1;pKa2=7.20;pKa3=12.38
TheyareallweakacidsandtheequationsfortheirdissociationsareshowninFigure3.
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Figure3a:Dissociationofsulfamicacid
Figure3b:Dissociationofformicacid
Figure3c:Dissociationofphosphoricacid
ThepKavalueisameasureofthestrengthofanacid(howeasilyaH+ionislost).The
largerthepKavalue,theweakertheacid.
Question2
Sulfamic,formicandphosphoricacidsareallweakacids.Explainthedifference
betweenaweakacidandastrongacid.
Question3
Whatisthesystematicnameofformicacid?
CillitBangLimeandGrime(2of2)
Weakacids
Imagineaweakacid,HA,whichdissociates
HA(aq) H+(aq)+A‐(aq)
Theequilibriumconstantisgivenby:
Kc=
[H  (aq) ] eqm [A  (aq) ] eqm
[HA (aq) ] eqm
Foraweakacid,thisisusuallygiventhesymbolKaandcalledtheaciddissociation
constant.
Ka=
[H  (aq) ] eqm [A  (aq) ] eqm
[HA (aq) ] eqm
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pKa=–log10Ka
(ThisisanalogouswithpH=‐log10[H+])
ThelargerthevalueofKa,thestrongertheacidandthegreatertheconcentrationofH+it
producesondissociation.However,becauseofthenegativesignintheexpression
above,thelargerthevalueofpKa,theweakertheacid.
Phosphoricacidhasthreeacidichydrogens(oneswhichcanbelostasH+ionsor
protons).
Figure4:Dissociationsofphosphoricacid
Question4
ExplainwhythepKavaluesgetlargerforthesecondandthirddissociationsof
phosphoricacid.
ThepKavaluesforthedissociationsshowthatitgetssuccessivelyhardertolosethe
secondandthirdH+ions.
Question5
a)Explainwhy,whenformicaciddissociates,thehydrogenatombondedtoan
oxygenatomistheonelostasaH+ionratherthantheonebondedtothecarbon
atom.
b)ThepKaofformicacidis3.8,whatisthevalueofKa?Givethecorrectunits.
c)WriteanexpressionforKaofformicacid(representtheacidasHCOOH).
d)CalculatethepHofa1moldm‐3solutionofformicacid.
e)CompareyouranswerforthepHofformicacidwiththatof1moldm‐3
hydrochloricacid(HCl),astrongacid.
Rust
Rustisnotasinglecompound.Itisaneverydaytermforamixtureofironoxidesand
hydroxidesformedbytheoxidationofironbyoxygenintheair,usuallywhenwateris
present.Probablythemostimportantconstituentisiron(III)oxidewithvarious
amountsofhydration(Fe2O3.nH2O)buttherewillalsobehydroxidessuchasiron(III)
hydroxide(Fe(OH)3).
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Question6
Ironalsoformsiron(II)oxideandiron(II)hydroxide.Givetheformulaeofthese
compoundsandsuggestwhytheyarelesslikelytobefoundinrustthanthe
correspondingiron(III)compounds.
Ruststainsarecommonbecausemanyeverydayitemsaremadefromiron.Theyare
unsightlybecauseiron(III)compoundsarebrown.
Figure5:Exampleofaruststainonfabric
Becausemetaloxidesarebasic,acid‐basedcleanersareusedtodissolveruststains.For
examplehydrochloricacid:
Fe2O3(s)+6HCl(s) 2FeCl3(aq)+6H2O(l)
Noticethatthestartingmaterialissolidandtheproductformsanaqueoussolution,thus
removingitfromthesurface.
Question7
Writeabalancedsymbolequationforthereactionofiron(III)hydroxidewith
hydrochloricacid.
Detergentsandsurfactants
Acid‐basedcleanersalsocontainsurfactantstolowerthesurfacetensionofwaterand
allowthemtospreadmoreeffectivelyoverdirtysurfaces.
Weusesurfactantstogetwaterandgreasetomix.Theyaremoleculesthatare‘tadpole
shaped’inthattheyhaveanon‐polar‘tail’andapolarorionic‘head’.The‘tail’canform
vanderWaalsbondswithnon‐polargreasemoleculeswhilstthe‘head’canform
hydrogenbondswithwater.Thisisanexampleofthe‘likedissolveslike’rule.
Thereareessentiallythreetypesofsurfactants‐anionic,cationicandnon‐ionic.
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Anionicsurfactantshaveanegativelychargedhead.Commontypesincludesoaps,
Figure6,andalkylbenzenesulfonates,Figure7.
Figure6:Sodiumstearate(asoap)–ananionicsurfactant
Figure7:Sodiumdodecylbenzenesulfonate–ananionicsurfactant
Cationicsurfactantshaveapositivelychargedhead.Commontypesincludealkyl
ammoniumchlorides.
Figure8:Trimethylhexadecylammoniumchloride–acationicsurfactant
Nonionicsurfactantshaveapolar,butuncharged,head.Commontypesinclude
polyethyleneethoxylates.
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Figure9:Apolyethyleneethoxylate–anonionicdetergent
Whendissolvedinwater,surfactantstendtoclusteratthesurface(hencethename),so
thattheirnon‐polartailscanstickoutofthewater.
Question8
LookatthemoleculesinFigures6‐9.Explainwhytheheadsarepolarandthetails
nonpolar.
CillitBangtoiletcleaners
Thesecleanersworkbybleachingstains.Theyarebasedaroundaformulation
containingsodiumhypochlorite(NaClO)andsodiumhydroxide(analkali).
Question9
Whatisthesystematicnameforsodiumhypochlorite?Hint,workoutthe
oxidationnumber(oxidationstate)ofthechlorineatom.
+1isanunusuallyhighoxidationstateforchlorine‐itisnormally‐1initscompounds.
Thismeansthatitcanactasanoxidisingagent,oxidisingotherspeciesasititselfdrops
inoxidationstate.Thisishowitbleachesandkillsgerms.
Theactualactiveingredientischloric(I)acid(HOCl)andisformedbythereaction
NaOCl(aq)+H2O(aq) Na+(aq)+OH‐(aq)+HOCl(aq)
Figure10a:Structureofsodiumchlorate(I),NaClO
Sodiumchlorate(I)isformedbythereactionofchlorinewithsodiumhydroxide
Cl2(g)+2NaOH(aq) NaOCl(aq)+NaCl(aq)+H2O(l)
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Figure10b:Structureofchloric(I)acid,HOCl
TheOH‐ionsfromthesodiumhydroxidewillalsobreakdowntheproteinsinhair,for
example,(whichoftenblocksthedrainsinbathsandwashbasins).
Limescaleisoftenfoundintoiletsanddrainsanditistemptingtoaddanacid‐based
cleanertoableach‐basedone.However,thefollowingequilibriumexistsinableach‐
andsodiumhydroxide‐basedcleaner.
ClO‐(aq)+Cl‐(aq) Cl2(g)+OH‐(aq)
AddedacidwillreactwiththeOH‐ionstoformwaterand,byLeChatelier´sprinciple,
theequilibriumwillmovetotherighttorestoretheconcentrationofOH‐,withthe
consequentformationofpoisonouschlorinegas.Notagoodidea!
Bleach‐basedcleanersalsocontainsurfactantstolowerthesurfacetensionofwaterand
allowthemtospreadmoreeffectivelyoverdirtysurfaces(seepreviouspage).Other
bleachingsystemsincludeonesbasedonpercarbonates(seeFinish).
CillitBangdegreasers(1of3)
Greaseessentiallyconsistsoffats.Fatsaretriglycerides,thatistheyareestersofthe
triolglycerol(propane‐1,2,3‐triol)andthreelongchainfattyacids(RCOOH),whereRis
ahydrocarbonchainofaround15carbonatoms,seeFigure11.
Figure11:Fatsareestersofglycerol
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Theyarerelativelynon‐polarandthereforedonotmixwellwithwaterwhichiswhat
makesthemdifficulttoremove.
Degreasingcleaners,forgreasystainsandbakedondirt,arebasedondetergentsand
surfactantsaswellassolvents.Theyaregenerallyformulatedtobealkaline.Greaseis
saponifiedunderalkalineconditions‐aprocessthatitselfremovesgreaseand
producessoapsthathelpanyremaininggreasetomixwithwater.
Hydroxideionsreactwiththemoleculesofgreaseandbreakthemupintosaltsoffatty
acidsandglycerol.ThereactionisshowninFigure12andisthesameasthatformaking
soapfromfatsandoils‐saponification.Theresultingsodiumsaltsoffattyacidsare
themselvessoapsandaidcleaning.
Figure12:Thesaponificationofgrease
CillitBangdegreasers(2of3)
OneformulationofCillitBangdegreaserincludesthefollowingactiveingredients(the
namesarenon‐systematic):



Along‐chainamineoxide
Ethanolamine
Glycolethers
Perfumeand,sometimes,dyeisalsoaddedtomaketheproductmoreattractivetothe
consumer.
We’lllookbrieflyatthechemistryandfunctionsofthesebelow.
Amineoxides
Amineoxides,Figure13,aresurfactants‐theyhavetheclassic‘tadpole‐shaped’
moleculewithapolarheadandanon‐polartail(seeDetergentsandsurfactants).The
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tailcanmixwithnon‐polargreasemoleculesandtheheadwithpolarwatermolecules
thuspromotingmixingofgreaseandwater.Italsoreducesthesurfacetensionofwater
andallowswaterto‘wet’surfacesmoreeffectively,thatistospreadoverthem.
Figure13:Structureofanamineoxide–thelengthofthehydrocarbonchainmayvary
Ethanolamine
Ethanolamineisasolvent.IthastheformulashowninFigure14.
H
N
H
H
H
C
C
H
H
O
H
Figure14:Structureofethanolamine
Question10
Whatisthesystematicnameofethanolamine?
Question11
a)Whattwofunctionalgroupsdoesethanolaminehave?
b)Whichofthesegroupsissignificantlybasic?
Aswellasactingasasolvent,ethanolamineraisesthepHoftheproduct,makingitmore
alkaline.
Question12
a)Writeanequationforthereactionofethanolaminewithwatertoshowhow
ethanolaminemakestheproductmorealkaline.
b)Whatfeatureoftheethanolaminemoleculemakesthisreactionpossible?
Question13
Theoxygenatomofethanolaminealsohasalonepairofelectrons.Explainwhyit
isthelonepairofelectronsonthenitrogenatomratherthanthatontheoxygen
atomthatisdonatedtoaproton.
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CillitBangdegreasers(3of3)
Glycolethers
Glycolphenylethersarewatersolublesolvents.Theypenetrategrease.Atypical
structureisshowninFigure15.
Figure15:Typicalstructureofaglycolether.Thisoneisaglycolphenyletherasithasabenzene
ring.Thealcoholfunctionalgroupisshowninthedottedovalandtheetherinthesolidoval
Todothis,theyshouldideallybenon‐polar,becausegreasemoleculesareessentially
non‐polar.However,theymustalsomixwithwaterasCillitBangdegreasersare
dispersedinaqueoussolution.Sothecompoundschosenmustbesufficientlypolarto
mixwithwater.
Glycolethers,whichhavebothanalcohol(R‐O‐H)andanether(R‐O‐R)group,havethe
rightdegreeofpolaritytodoboth.Theseconsiderationsaresimilartothosethatapply
tosurfactantsdescribedabove.Theymustalso,ofcourse,havenodamagingeffectson
thesurfacesonwhichtheywillbeused.
Figure16:CillitBangPowerCleanerDegreaser
CillitBangisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.
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Furtherinformation
TheCillitBangfamilyofcleanersaresoldbyReckittBenckiser(www.cillitbang.co.uk).
CillitBangisaregisteredTradeMarkofReckittBenckiserNV.Thereareotherbranded
productswhichworkinasimilarway.
Acknowledgements
TheRoyalSocietyofChemistrywishestothankChrisJones,CandiceTaylor,EdCooney
andFaridNekmardofReckittBenckiserforhelpinpreparingthismaterial.
TheRoyalSocietyofChemistrygratefullyacknowledgesthatthisprojectwasinitially
supportedbyReckittBenckiserin2007.ReckittBenckiserconductedafinalreviewin
2013sopleasenotethatcertaininformationmaybeoutofdate.
QUESTIONSANDANSWERS
Question1
Givetworeasonswhythecalciumcarbonatedepositformsmorereadilyonthe
hottapofasinkratherthanthecoldone.
Theheatevaporatesthewater.Inhotconditions,LeChatelier’sprinciplepredictsthat
theequilibriummovestotheleft,thedirectioninwhich∆Hispositive,iethereactionis
absorbingheatandcoolingthesurroundings.
Question2
Sulfamic,formicandphosphoricacidsareallweakacids.Explainthedifference
betweenaweakacidandastrongacid.
Weakacidsareonlypartiallydissociatedinsolution.Strongacidsarecompletely
dissociatedinsolution.
Question3
Whatisthesystematicnameofformicacid?
Methanoicacid
Question4
ExplainwhythepKavaluesgetlargerforthesecondandthirddissociationsof
phosphoricacid.
ThepKavaluesareameasureofthestrengthoftheacids(howeasilyaH+ionislost).
ThebiggerthepKavalue,theweakertheacid.Itishardertolosethesecondprotonthan
thefirstbecauseitisbeinglostfromasinglynegativelychargedionratherthana
neutralmolecule.Itishardertolosethethirdprotonthanthesecondbecauseitisbeing
lostfromadoublynegativelychargedionratherthanasinglychargedone.
Question5
a)Explainwhy,whenformicaciddissociates,thehydrogenatombondedtoan
oxygenatomistheonelostasaH+ionratherthantheonebondedtothecarbon
atom.
Oxygenissignificantlymoreelectronegativethanhydrogen(3.5asopposedto2.1).So
theO‐HbondispolarisedOδ‐‐Hδ+makinglossofthehydrogenasH+easy.Carbon’s
CillitBangisaregisteredtrademarkoftheReckittBenckisergroupofcompanies.
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electronegativityissimilartothatofhydrogen(2.5to2.1)sotheC‐Hbondisrelatively
non‐polarandthereislittletendencyfortheHatomtoacquireapositivecharge.
b)ThepKaofformicacidis3.8,whatisthevalueofKa?Givethecorrectunits.
pKa=‐log10KasoKa=1.6x10‐3moldm‐3
c)WriteanexpressionforKaofformicacid(representtheacidasHCOOH).
Ka=
[H  (aq) ] eqm [HCOO  (aq) ] eqm
[HCOOH(aq) ] eqm
d)CalculatethepHofa1moldm‐3solutionofformicacid.
[HCOO‐(aq)]eqm=[H+(aq)]eqm
[HCOOH(aq)]eqm=1‐[H+(aq)]eqm≈1(wecansafelymakethisassumptionforaweakacid)
So1.6x10‐3=
[H  (aq) ] 2 eqm
1
[H+(aq)]eqm=√(1.6x10‐3)=0.04moldm‐3
pH=–log10[H+(aq)]eqm=1.4
e)CompareyouranswerforthepHofformicacidwiththatof1moldm‐3
hydrochloricacid(HCl),astrongacid.
Hydrochloricaciddissociatescompletelyinsolution
HCl(aq) H+(aq)+Cl‐(aq)
So[H+]eqm=1moldm‐3
pH=–log10[H+(aq)]eqm=0
Question6
Ironalsoformsiron(II)oxideandiron(II)hydroxide.Givetheformulaeofthese
compoundsandsuggestwhytheyarelesslikelytobefoundinrustthanthe
correspondingiron(III)compounds.
FeO;Fe(OH)2.Oxygenintheaircanoxidiseiron(II)toiron(III).
Question7
Writeabalancedsymbolequationforthereactionofiron(III)hydroxidewith
hydrochloricacid.
Fe(OH)3(s)+3HCl(aq) FeCl3(aq)+3H2O(l)
Question8
LookatthemoleculesinFigures6‐9.Explainwhytheheadsarepolarandthetails
nonpolar.
Ineachcase,theheadcontainselectronegativeatomswhichcanparticipateinhydrogen
bondingwithwater.Inthefirstthreecases,theheadshaveioniccharges.Thetails
consistofhydrocarbonchainswhichcannotformhydrogenbonds.
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Question9
Whatisthesystematicnameforsodiumhypochlorite?Hint,workoutthe
oxidationnumber(oxidationstate)ofthechlorineatom.
Sodiumchlorate(I).Theoxidationnumberofthesodiumis+1andthatoftheoxygenis–
2.Sotokeepthesumoftheoxidationnumbersinaneutralcompoundequaltozero,that
ofthechlorinemustbe+1.Hint‘ate’inachemicalnameusuallymeans‘andoxygenas
well’.
Question10
Whatisthesystematicnameofethanolamine?
2‐aminoethanol.
Question11
a)Whattwofunctionalgroupsdoesethanolaminehave?
Primaryamineandprimaryalcohol.
b)Whichofthesegroupsissignificantlybasic?
Primaryamine.
Question12
a)Writeanequationforthereactionofethanolaminewithwatertoshowhow
ethanolaminemakestheproductmorealkaline.
H2NCH2CH2OH+H2O H3N+CH2CH2OH+OH‐
b)Whatfeatureoftheethanolaminemoleculemakesthisreactionpossible?
Alonepairofelectronsonthenitrogenatom.
Question13
Theoxygenatomofethanolaminealsohasalonepairofelectrons.Explainwhyit
isthelonepairofelectronsonthenitrogenatomratherthanthatontheoxygen
atomthatisdonatedtoaproton.
Nitrogenislesselectronegativethanoxygen(ithasonelessprotoninitsnucleus)soits
lonepairislessstronglyheldandmoreeasilydonatedtoaproton.
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