4. Complexometric Titration

A. T TIITLE B. PURPOSE

: Complexometry Titration and its Application determine (standardizati (standardization) on) of Na-EDTA Na-EDTA : 1. To make and determine

solution . To determine t!e total !ardness of "en#eran $ell $ater C. BASIC BASIC TH THEO EORY RY :  Complexometry Titration Complexomet Complexometric ric titration titration (sometimes (sometimes c!elatometry) c!elatometry) is a form of %olumetric analysis in analysis in $!ic! t!e formation of a colored complex is used to indicate t!e end point of a titration. Complexometric titrations are particularly useful for t!e determination of a mixture of different metal ions in solution. An indicator capa&le capa&le of producin' an unam&i'uous color c!an'e is usually used to detect t!e end-point of t!e titration. asi asicc t!eo t!eory ry of compl complexo exome metr try y titr titrat atio ion n $it! $it! EDT EDTA is t!e t!e form formin in' ' of complex compound &et$een some metal (suc! as Ca* +'* Ni* ,n* Cu* etc) $it! EDTA. +etals $ill forms complex $it! EDTA at different p* Ca  and +' react $ell at p / 0 1. EDTA (Etilen Diamine Tetra Acetate) is an acid &ase 2 ( 23). &ut* $!ic! is often used is t!e natrium salt (Na3). t!e formin' of complex &et$een metals ions and EDTA accordin' to p of solution. 4ndicator t!at is used are ET (Enoc!rome lack T) and "al'amit. T!at indicator is a $eak acid &asic 5 (54n). dissociatin' e6uili&rium of t!at indicator $ill 'i%e some colors and formin' complex 1  1 $it! total metal ion* so* can 'i%e t!e color c!an'e at t!e end of reaction. Reactions  

: 4n- 4n-   7ed lue !it" metal ion : Ca* +'* ,n* Ni +'  4n- +'4N-   7ed 'rape  +'3- +'3  4n5!it" E#TA : +'4n  3 7ed 'rape 4n5-  8 4n-  8lue At e$%i&alent point: 9um of e6ui%alent +' : sum of e6ui%alent EDTA Inicator

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Complexometry Titration

1

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9o* t!e c!an'in' color t!rou'! titration is  solution t!at contain of metal ion like t!e statement a&o%e after added &y ET indicator $ill &e c!an'e into red 'rape* after t!at* after t!ere;s !appen an e6ui%alent &et$een metal ion $it! EDTA can &e seen from t!e form of &lue from indicator in 4n-. 4n t!eory* any complexation reaction can &e used as a %olumetric tec!ni6ue pro%ided t!at 1. T!e T!e react reactio ion n reac reac!e !ess e6uili&rium e6uili&rium rapidly rapidly after eac! portion of titrant is added. . 4nterf 4nterferi erin' n' situatio situations ns do not arise. arise.
Rea'ent E#TA

EDTA** et!ylenediaminet EDTA et!ylenediaminetetraac etraacetic etic acid* !as four car&oxyl car&oxyl 'roups and t$o amine 'roups 'roups t!at can act as electron electron pair donors* donors* or =e$is &ases. &ases. T!e a&ility of EDTA EDTA to potent potential ially ly donate donate its its six lone pairs pairs of electr electrons ons for t!e format formation ion of coordi coordinate nate co%alent co%alent &onds to metal metal cation cationss makes makes EDTA EDTA a "exaentate li'and. o$e%er* in practice EDTA is usually only partially ionized* and t!us forms fe$er t!an six coordinate co%alent &onds $it! metal cations. Disodi Disodium um EDTA EDTA is common commonly ly used used to standa standardi rdize ze a6ueous a6ueous soluti solutions ons of transition metal cations. Disodium EDTA (often $ritten as (a H Y) only forms four











amine 'roups remain protonated and t!us una&le to donate electrons to t!e formation of coordinate co%alent &onds. Note t!at t!e s!ort!and form (a*+xHxY can &e used to repres represent ent any specie speciess of EDTA EDTA* $it! $it! x desi'natin' t!e num&er of acidic protons &onded to t!e EDTA molecule. EDTA forms an octa!edral complex $it! most  metal cations* +* in a6ue a6ueous ous solu soluti tion. on. T!e T!e main main reas reason on t!at t!at EDT EDTA is used used so exten extensi si%e %ely ly in t!e t!e standardization of metal cation solutions is t!at t!e formation constant for most metal cation-EDTA complexes is %ery !i'!* ! i'!* meanin' t!at t!e e6uili&rium for t!e reaction +  23 ? +3   lies far to t!e ri'!t. Carryin' out t!e reaction in a &asic &uffer solution remo%es  as it is formed* $!ic! also fa%ors t!e formation of t!e EDTA-metal cation complex reaction product.
To carry out metal cation titrations usin' EDTA* it is almost al$ays necessary to use a complexometric indicator to indicator to determine $!en t!e end point !as &een reac!ed. Common indicators are or'anic dyes suc! as










t!e metal ion lea%in' ET $!ic! formed $eak and unsta&le compound react $it! EDTA forms sta&le and sta&le complex. !ell !ater

9!allo$ pumpin' $ells can often supply drinkin' $ater at at a %ery lo$ cost* &ut &ecause impurities from t!e surface easily reac! s!allo$ sources* a 'reater risk of contamination occurs for t!ese $ells $!en t!ey are compared to deeper $ells. C!emical C!emical contamination contamination is a common pro&lem $it! 'round$ater. 'round$ater. Nitrates from se$a'e or fertilizer are a particular pro&lem for c!ildren. ollutant c!emicals includ includee pesticides and %olatile or'anic compounds compounds from 'asoline 'asoline** dry-cleanin' dry-cleanin'** t!e fuel additi%e met!yl tert-&utyl et!er (+TE)* et!er (+TE)* and perc!lorate and perc!lorate from from rocket fuel* air&a' inflators* and ot!er artificial and natural sources. 9e%eral 9e%eral minerals are also contaminants contaminants** includin' lead lead leac!ed from &rass fitt fittin in's 's or old old lead lead pipe pipes* s* c!rom c!romium ium B4 from electroplatin' electroplatin' and ot!er sources* naturally occurrin' arsenic arsenic** radon radon** and uranium all of $!ic! can cause cancerand naturally naturally occurrin' occurrin' fluoride fluoride** $!ic! $!ic! is desira&le desira&le in lo$ 6uantiti 6uantities es to pre%en pre%entt toot! decay** &ut can cause dental fluorosis in decay fluorosis in !i'!er concentrations./ 9ome c!emicals are commonly present in $ater $ells at le%els t!at are not toxic* &ut can cause ot!er pro&lems. Calcium Calcium and and ma'nesium ma'nesium cause cause $!at is kno$n as !ard $ater * $!ic! can precipitate and clo' pipes or &urn out $ater !eaters. 4ron and man'anese can appear as dark flecks t!at stain clot!in' and plum&in'* and can man'anese promote t!e 'ro$t! of ir iron on and man man'ane 'anese se &act &acteri eriaa t!at can form slimy &lack colonies t!at clo' pipes.











ard Fater@ ardness Fater ard ard $ater $ater is $ater t!at t!at !as !i'! !i'! mineral content (in contrast $it! Gsoft Gsoft $ater G). G). ard drinkin' $ater is is 'enerally not !armful to oneHs !ealt!*1 &ut can pose serious pro&lems in industrial settin's* $!ere $ater !ardness is monitored to a%oid costly &reakdo$ns in &oilers in &oilers** coolin' to$ers* to$ers* and ot!er e6uipment t!at !andles $ater. 4n domestic settin's* !ard $ater is often indicated &y a lack of suds formation $!en soap is a'itate a'itated d in $ater* $ater* and &y t!e formatio formation n of limescale limescale in kettles and $ater !eaters. F!ere%er $ater !ardness is a concern* $ater softenin' is softenin' is commonly used to reduce !ard $aterHs ad%erse effects. FaterHs !ardness is determined &y t!e concentration of multi%alent cations in t!e $ater. +ulti%alent cations are cations (positi%ely c!ar'ed metal complexes) complexes) $it! a c!ar'e 'reater t!an 1. Isually* t!e cations !a%e t!e c!ar'e of . Common cations found in !ard $ater include Ca and +'. T!ese ions enter a $ater supply &y leac!in' leac!in' from minerals minerals $it!in an a6uifer . Common calcium calcium-containin' -containin' minerals are calcite and calcite and 'ypsum 'ypsum.. A common ma'nesium ma'nesium mineral mineral is dolomite dolomite ($!ic! ($!ic! also contains calcium). 7ain$ater and and distilled distilled $ater $ater are soft soft** &ecause t!ey contain fe$ ions ions.. T!e T!e foll follo$ o$in in' ' e6uili e6uili&rium &rium react reaction ion desc descri ri&e &ess t!e t!e dissol%in' dissol%in'@form @formation ation of calcium car&onate scale scale CaC85  C8  8 J Ca  C85K Calcium car&onate scale formed in $ater-!eatin' systems is called limescale limescale.. Calcium and ma'nesium ions can sometimes &e remo%ed &y $ater softeners. softeners.











Temporary !ardness is a type of $ater !ardness caused &y t!e presence of dissol%ed &icar&onate minerals (calcium &icar&onate and ma'nesium &icar&onate). &icar&onate). F!en dissol%ed dissol%ed t!ese minerals yield calcium and ma'nesium cations (Ca* +') and and car&o car&onat natee and and &icar&onate anions (C85-* C85-). T!e presence of t!e metal cations cations makes t!e $ater !ard. o$e%er* o$e%er* unlike t!e permanent !ardness !ardness caused &y sulfate and sulfate and c!loride compounds compounds** t!is GtemporaryG GtemporaryG !ardness !ardness can &e reduced eit!er &y &oilin' t!e $ater* or &y t!e addition of lime (calci calcium um !ydrox !ydroxide ide)) t!ro t!rou' u'! ! t!e t!e softeni softenin' n' proces processs of lime softenin'. softenin'. oilin' promotes t!e formation of car&onate from t!e &icar&onate and precipitates calcium car&onate out of solution* lea%in' $ater t!at is softer upon coolin'.

#. Tools an materials : Bolumetric flask L m= ipette Bolumetric pipette Erlenmeyer urette CaC85 A6uades Cl Na-EDTA solution M *1 + CaCl solution ET













E. PROCE#URE : #etermination o, stanari-ation (a+E#TA sol%tion  /0/1 2 3it" CaCl

)

as stanar sol%tion

- +o%ed ± 0,4 grams of into t!e %olumetric flask L m= used $ater M 1 -

m= Added Cl 1  1 drop &y drop until 'ladak 'as stopped Diluted $it! $ater until t!e limit si'n 9!ake until mixed perfectly Fas!ed and filled $it! Na-EDTA solution M *1 + ipette $it! %olumetric pipette L m= of CaCl solution Entered into t!e Erlenmeyer 5 m= Added L m= of &uffer solution p 1 Added L drops of ET indicator Titrated $it! Na-EDTA solution *1 + 9topped titration $!en t!ere;s c!an'in' color from redis! 'rape to &lue

Changing- Color 7ead and note t!e num&er on &urette $!en t!e first and t!e

-

end of titration Determine and note Na-EDTA solution t!at used in titration Calculated t!e mean concentration of Na-EDTA

The mean











(l)e *preio)sly )ntil re+ - olor

-

Calculated t!e sum of t!e !ardness in CaC85 salt per liter of $ater (in t!e form of ppm)

$erage har+ness of &ell &ater











6. E7PERI2E(T RESULT (o . 1.

:

Proce%re o, Experiment

Determination of standardization Na-EDTA solution M *1 + $it! CaCl as standard solution ± 0,4 grams of

-

+o%ed into t!e %olumetric flask L m= used $ater M

-

1 m= Added Cl 1  1 drop &y drop until

-

'ladak 'as stopped Diluted $it! $ater

-

until t!e limit si'n 9!ake until mixed

perfectly - Fas!ed and filled $it! Na-EDTA

-

solution M *1 + ipette $it! %olume-

Experiment res%lt Be,ore: CaCO3 po&+er.&hite

Hypot"esis CaC85(s) 8(l)

Na-EDTA CaC85



Cl sol)tion. olorless ()ersol)tion. olorless "(T n+iatior. +ar p)rple *re+ &ine !a-"#T$. olorless After:

CaCO3 sol)tion. t)ri+ ()er sol)tion CaCl2. olorless

concentration is .1 +

(a6) .

$/)a+es .olorless

Concl%sion

CaC85(s) Cl(a6)

CaCl(



a6)C8(')  8(l) Ca32- Ca3











3"#T$. 73 m%

-

ET indicator Titrated $it! NaEDTA solution *1

-

+ 9topped titration $!en t!ere;s c!an'in' color from redis! 'rape to &lue

Changing 7ead and note t!e - Color

num&er on &urette $!en t!e first and

-

t!e end of titration Determine and note Na-EDTA solution

-

t!at used in titration Calculated t!e mean concentration of NaEDTA

The mean onentration of !a-











()ersol)tion. olorless

-

ipette and dropped

-

to Erlenmeyer Added  m= &uffer

-

solution p 1 Added 5 drops of

"(T n+iatior. +ar p)rple *re+ &ine

-

ET Titration $it! EDTA

!a-"#T$. olorless

5x

(l)e *preio)sly )ntil re+ olor

-

Calculated t!e sum of t!e !ardness in CaC85 salt per liter of $ater (in t!e form of ppm)

The aerage har+ness har+ness &ater of &ell &ater

After:

()er sol)tion &ell &ater. olorless ()er sol)tion &ell &ater"(T. re++ish grape $fter titrate+ y !a-"#T$. re++ish grape to l)e 1"#T$.1 ' m% 2"#T$. 22 m% 3"#T$. 20 m%

ken#eran is 1. ppm













8. A(ALY A(ALYSIS A(# #ISCUSSIO( #ISCUSSIO( a. #ete #etermi rminat nation ion o, Stan Stanar arii-ati ation on (a+E (a+E#T #TA A  /0/1 /0/1 2 3it" 3it" CaCO CaCO 9 as primery stanar sol%tion. 4n t!e experiment t!at $e !a%e done* $e used */1 'rams of $!ite

po$der CaC85* t!en $e poured into %olumetric flask* t!en $e add a6uadest. T!e reaction t!at occur is  CaC85(s)  8(l) CaC85(a6) . After t!at $e add Cl +* 11 drops &y drops until t!e &u&&les 

disappear (C8 lose). And t!en $e dilute dilute $it! a6uadest a6uadest a'ain until until formed formed CaCl solution. T!e reaction t!at occur in t!is step is  CaC85(s)   Cl(a6) CaCl(a6)  C8(')  8(l) To kno$ t!at C8 is lose $e o&ser%e $it! t!ere is c!an'es from tur&id 

&ecome clear solution. After t!at $e pipette 1 ml of CaCl solution 1ml of &uffer solution. And $e add  drops of ET indicators. 4n t!e &asic* t!is titration formed complex ions* Ca $it! EDTA. EDTA EDTA is a c!elati c!elatin' n' a'ent a'ent t!at t!at can donate donate electr electrons ons (=e$is (=e$is rule) $!ic! $ould t!en form a complex $it! t!e metal ion (=e$is acid). EDTA $ill











Fit! Fit! metallic ion Ca so it &ecome Ca  in-

Ca4n-   7ed $ine Ca3- Ca3  4n5

Fit! EDTA  Ca4n-  37ed Fine 4n5-  8 



4n-  8-



lue T!en t!e solution titrated $it! Na-EDTA. Fe stopped $!ere t!ere is c!an'es of color from red $ine &ecome &lue. T!e reaction t!at occur is  Ca  32- Ca3T!e &lue color t!at occur due to titrant is a mixture of +'3 - and 32-. 

F!en !en

t!e mixtu ixturre

t!e more- sta&le $ill

$as $as adde added d to a &e

formed &y

solut olutio ion n cont contai aini nin' n' Ca* Ca3free +'

to react $it! t!e

indicator (ET) and- form red +'4n-. After t!e calcium calcium is used in full* full* additional additional titrant titrant c!an'e c!an'e +'4n +'4n- and +'3 indicator turns into a &lue 4n-form. 4n t!is experiment $e 'ot Na-











. #eterminin' #eterminin' Tota Totall Harness Harness O, !e !ell ll !ater !ater..

4n t!e determinati determination on total !ardness !ardness of $ell $ell $ater* $ater* pipette pipette 1 m= of $ell $ater and mo%ed into Erlenmeyer L m=* t!en add 1 m= of &uffers solution p 1 in t!e form of clear colorless solution and  drops of ET indicator $it! t!e red 'rape color. T!en titrated $it! Na-EDTA solution until t!e analyte solution c!an'ed color into &lue. T!e c!an'e color into &lue it s!o$ t!at t!e end point titration is reac! . 7epeat t!e experiment 5 times t!an $e can 'et t!e a%era'e total !ardness $ater . Isin' e6uation  mmol sample : mmol EDTA Fe 'ot mmol $ell $ell $ater sample sample $!ic! are used to determine determine t!e mass of Ca. +ass Ca o&tained is used to determine t!e !ardness of $ell $ater &y di%ided mass of Ca ('r) and $ell $ater %olume (sample %olume)(l).











I. A(S! A(S!ER ER O6 ;UES ;UESTI TIO( O( 2a o, (a+E#TA sol%tion. 1> 6in t"e t"e c"emical c"emical ,orm%la ,orm%la o, (a+E#TA0 (a+E#TA0 Blac< Blac< Erio
T!e c!emical formula of lack Eriokrom T is











9> Ho3 to ma
N28  N2Cl → &uffer k b  Basa 

Garam -

8 

: k b D NH 2 OH E

D NH 2 Cl E

: 1*/ x 1

−L

x D NH 2 OH E

D NH 2 Cl E

:













D NH 2 OH E

1*/ x 1

D NH 2 Cl E

1

−2

: gr

D NH 2OH E

Mr . V

: gr 5L . V

1*/ x 1-L

:

*5 x 1-2 B :

'r

−L











). A 1// mL o, samp sample le 3ater 3ater contain containin' in' ions ions Ca ) an 2' ) is titrate 3it" 1.) mL o, /./1/1D 2 E#TA in an ammonia %,,er pH 1/. Anot"er example is 1// mL titrate 3it" (aOH to precipitate precipitate 2' =OH> ) an t"en titrate to pH 19 3it" 1/.*9 mL o, t"e same E#TA sol%tion. Calc%late "o3 ppm CaCO9 an 2'CO9 in t"e sample@ Ans3er: "no$n 

BEDTA 1 :

1L*/ m=

+EDTA B

:

*11 + 1 25 =











 ppm

+'C85

mmol +'C85:mmol EDTA : + x (B1 0 B) EDTA :*11 x 2*/L :*2P5 mmol m' +'C85:mmol x +r :*2P5 x /2











. RE6ERE(CE usain* Asif. O. T!eoritical asis of Analysis Complexometric Titration. Ne$ Del!i !ttp@@amrita.%la&.co.in@ Accessed !ttp@@amrita.%la&.co.in@ Accessed on +onday* Decem&er 1t! 15 !ttp@@en.$ikipedia.or'@$iki@ComplexometricQtitration** Decem&er 1t! 15 !ttp@@en.$ikipedia.or'@$iki@ComplexometricQtitration !ttp@@en.$ikipedia.or'@$iki@FaterQ$ell Accessed !ttp@@en.$ikipedia.or'@$iki@FaterQ$ell Accessed on
Tim.15.anduan raktikum "imia Analitik 4 Dasar-Dasar "imia Analitik. 9ura&ayaRurusan "imia <+4A INE9A











4. ATTACH2E( CH2E(T T PICTURE

E7PLA(ATIO(

Detrminin' 9tandarization Na-EDTA 9olution M.1+ Fit! CaCl As rimary 9tandard 9olution CaCl) a,ter a,ter ain' ain' y Eric"ro Eric"rome me Blac< T =EBT>













!ell !e ll !ater ater a,ter a,ter titrat titrate e y (a+ (a+ E#T E#TA sol% sol%tio tion n it c"an c"an'e 'e eca ecame me











L. CALC CALCUL ULA ATIO( IO( #eterminin' stanari-ation (a+E#TA sol%tion  /./1 3it" CaCl) as primary stanar sol%tion.











5. At B EDT EDTAO.5 O.5 m= m= mmol CaC85 : mmol EDTA +1. B1 : +.B











:.5 x 1-5 x 1. x 1- x 1 :.5 x 1-5 ' :.5 m' mass ( mg ) 2.3

4. Complexometric Titration

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