4.Titrimetric Analysis. Acid_Base Titration

8/17/2019 4.Titrimetric Analysis. Acid_Base Titration

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Analisis titrimetriAnalisis titrimetri

titrasititrasi asamasam basa.basa.


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Hal yang akan dipelajari

1. Metoda Titrimetri : konsep dasar dan klasifikasi.

2. Teknik dr titrimetri analisis.

3. Tipe dr penentuan titrimetri

4. Perhitungan dalm analisis titrimetri

5. Titrasi asam–basa metoda neutralisasi!: konsep

dasar" titran" definisi substan#es.

$. Pemilihan %ndikator perhitngan kesalah dlm titration.

&. Titrasi asam basa dlm pelarut non air


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1. Metoda analisis Titrimetri : konsep

dasar dan klasifikasi.

• Titrimetri – suatu metoda dimana volume

merupakan signal.

• Titrimetri , kita mengukur sejumlah volume dr

reagen yang b’reaksi secr stoikiometri dgnanalit.


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Prinsip dasar metodatitrasi :

1. Reaksi harus stoikiometri

2. Reaksi harus berlangsung cepat

3. Tidak ada reaksi samping

4. Harus terjadi perubahan ketika reaksitelah sempurna. (indikator

!. Terdapat titik ekui"alen

#. Reaksi harus kuantitati$


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angkaian Titrasi : titran ditambhkn dr buret ke lart analit dalam gelas

erlenmeyer. !danya indikator menunjukkan perub "arna secr

permanen yg menunjukkn titik akhir.


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Titrasi larutan asam yg tdk diketahui konsentrasinya degn

larutan basa yg diketahui secara pasti konsentrasinya


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• Titration adl suatu prosedur penentuan konsentrasi suatu

larutan dengan membiarkan se'umlh tertentu (olumebereaksi dengan suatu larutan standard )ang

konsentrasin)a telah diketahui se#ara pasti.

• Standardisasi adalah suatu proses memastikan suatu

teknik standar

•

%n #hemistr)" aliquot adlh toatal 'umlah suatu larutan.


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• Titrant # the reagent added to a solution containing the

analyte and "hose volume is the signal.

• ! reagent, called the titrant , of kno"n concentration $a

standard solution% and volume is used to react "ith a

solution of the analyte, "hose concentration is not

kno"n.

• equivalence point & titik ketika terjadi stoikiometri 'reaksi berjalan ekuivalen antara sejumlah analit dan titran.


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• End point * the point in a titration "here "e stop adding

titrant.

• Indicator * a colored compound "hose change in color

signals the end point of a titration.

• Titration error * the determinate error in a titration due tothe difference bet"een the end point and the e(uivalence

point.

• standar primar mrpk suatu standar $material% sangat

murni yang tidak perlu dikalibrasi oleh standar lainnya.


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• Standar Sekunder – suatu reagen yang kemurniannyaharus dipastikan terhadap standar'reagen primar.

• A burette (also buret) is a vertical cylindrical piece oflaboratory glass"are "ith a volumetric graduation on its

full length and a precision tap, or stopcock, on the bottom $or calibrated glass tube%.

• )ven the thickness of the lines printed on the burette

matters* the bottom of the meniscus of the li(uid should be touching the top of the line you "ish to measure from.


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stop#o#k buret


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+uret dengan botol berisi larutan standar

+uret ay#-ussac

+ t ith bb


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+uret ,ith rubber

shutter

+uret Mohr


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Mi#roburet:

-! hilo( air*po,ered +uret/ 0! stop#o#k buret


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• Pipet $juga disebut pipet, pipettor or chemicaldropper % adl suatu instrumen laboratori yg

digunakan untuk memindahkan sejumlh volumelarutan


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elas )rlenmeyer


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Terdapat bbrp cara utk menyiapkan

larutan standar :

Menimbang sample se#ra a##urat primarstandar!

b) means of standard substan#e or astandard solution se#ondar) standard!

standard titrimetri# substan#e primar)standard!


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A##uratel) ,eighed sample primar)

standard!

arena glas volumetri berisi suatu larutan, sangat pentinguntuk menyiapkan larutan dengan konsentrasi yg eksak.

eagent $the accurately "eighed sample% dipindahkn ke

glas volumetri, dan sejumlh pelarut ditambhkn utk

melarutkn reagen. /etelah semua reagent terlarut, pelarut

ditambhkan secara proporsional sampai tercapai volume

secara fi0. The final adjustment of volume to the flask’s

calibration mark is made using a dropping pipet. Tocomplete the mi0ing process, the volumetric flask should

be inverted at least ten times.


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olumetri# flask

olumetric flask 2 for preparing

li(uids "ith volumes of high precision.

3t is a flask "ith an appro0imately

pear#shaped body and a long neck "ith

a circumferential fill line.


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6erhitungan konsentrasi standar primer

3M

m4

M

⋅

V m

E

m

N

C =

35 mT


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• secondary reagent * a reagent "hose purity

must be established relative to a primary reagent

• To prepare the solution "e place calculated

amount of substance, "eighed to the nearest

tenth of a gram, in a bottle or beaker and add

appro0imately volume of "ater

b) means of standard substan#e or ab) means of standard substan#e or a

standard solutionstandard solution se#ondar) standard!se#ondar) standard!


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7

11

73

344

6

6

⋅

=

7! mengukur (olume dr larutan

standar primer lain

Memastikn konsentrasi standar sekunder Memastikn konsentrasi standar sekunder

"here:6262 and 22 are concentration and volume

of secondary standard solution

6161 and 11 are concentration and volume

of primary standard solution


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+% Menimbang sejumlh tertentu standar primer

38

m4

m

6⋅

⋅

=1888

"here:

6 and are concentration

and volume of secondary standard

solution

m and 8m are mass and

e(uivalent "eight of primarystandard


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Typical

instrumentation for

performing anautomatic titration.

4ourtesy of 9isher

/cientific.


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/uatu standar primar harus :

1. Hrs merupakn crystal structure and berhubungandgn formula kimia

7. High purity $it is the absence of impurity in a

substance%

. /tability $lo" reactivity%, baik pada suhu kamr or

ketika dipanaskan.

;. -o" hygroscopicity and ef#florescence $in chemistry,

is the loss of "ater $or a solvent% of crystalli


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=. High solubility $if used in titration%

>. High e(uivalent "eight.?. @ot to contain e0traneous impurity more than

admissible borders for substances of mark

Achemically pureB.C. Methods of purification of standard substance from

impurity $crystallisation, e0traction, sublimation

etc.% should be available in analytical laboratory.


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+eberapa conto st primar $)uropean 6harmacopoeia% :

• Arsenic trioxide ArO3 utk m’buat sodium arsenite solution

for standardisation of sodium periodate solution $also for

iodine and cerium $3% sulfate solutions, since 7887

standardised by sodium thiosulfate%

• +en


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Astandard titrimetric substanceB

$primary standard%

• More often in an

ampoule #ontains 9"1

mol 9"1 eui(alents!of substan#es" it is

ne#essar) for

preparation of 9"1mol; solution.


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Preparation rules primar) solutionsand definition of their titre.

1. The initial substance "hich is used for preparation of a standard solution, should bechemically pure.

7. The initial substance should easily and quicklyreact "ith standarti


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=. Titration process should end quickly andaccurately. The end point of titration should "ill bedefined easily and precisely.

>. To establish of titre it is desirable either a methodof accurately "eighed sample or dissolution of precisely "eighed initial substance in certainvolume.

?. 9or the prevention of errors by titration it isnecessary to choose volume of the primarystandard ali(uot or "eighed of standard substance,

that the volume of the secondary standard "hich"ill react in titration "as not less than 78 m- $bureton 7= m-% or ;8 m- $buret on =8 m-%.


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C. Titration should be carry out until then it "ill not be

received yet three reproduced results.

G. 6repared of standarti


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Metoda titrimetri dibagi menjadi ; tipe.

• a#id–base titrations, in "hich an acidic or basic

titrant reacts "ith an analyte that is a base or an acid*

•

#omple


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equirements to reactions in titrimetric analysis

• all reactions involving the titrant and analyte must be of

kno"n stoichiometry, quantitatively

• the titration reaction must occur rapidly

• a suitable method must be available for determining the

end point "ith an acceptable level of accuracy

• eactions should proceed b) room temperature

•Titration should not be accompanied by collateralreactions "hich deform the results of the analysis

• eactions should be speci!ic


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7. Techni(ues of titrimetric analysis.

• =ashing up and dr)ing ,are

• Preparation of standard solutions

•

ample preparation• Titration:

* Measurement of (olumes

* An indi#ator #hoi#e• al#ulations


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4ontoh umum glass"are yg digunakan utk m’ukur

volum :

>raduated #)linders

beaker

(olumetri# flask

measuring pipet

transfer pipet/


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4alibration: volumetric !lask # an injection method

pipettes, burettes # a pouring out method


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Methods to determine the end point

• visual indicators" Colour change: 3n some reactions, the solution changes colour "ithout

any added indicator . This is often seen in redox titrations, for instance,"hen the different o0idation states of the product and reactant producedifferent colours.

recipitation! 3f the reaction forms a solid, then a precipitate "ill formduring the titration. ! classic e0ample is the reaction bet"een !gI and4l# to form the very insoluble salt !g4l. This usually makes it difficultto determine the endpoint precisely. !s a result, precipitation titrationsoften have to be done as JbackJ titrations $see belo"%.

• Physical and chemical methods "ith the subse(uent analysis of curvesof the titration sho"ing changes "hich occur in the course of titration$change of physical and chemical parametres standard solutions%


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. Tipe penentuan dlm titrimetri.

Titration #an be:

•

dire#t titration • ba#k*titration on residue!

• substitute*titration displa#ement titration!

• re(erti(e titration

di t tit ti i dd l l i d i h


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direct titration & titrant add to an analyte solution and react "ithdetermined substrance

?euirements to rea#tions in dire#t titration

• reaction involving the titrant and analyte must be ofkno"n stoichiometry, quantitatively

• the titration reaction must occur rapidly

•a suitable method must be available for determining theend point "ith an acceptable level of accuracy

• eactions should proceed b) room temperature

• Titration should not be accompanied by collateral

reactions "hich deform the results of the analysis

• eactions should be speci!ic

• a suitable indicator is a"aila#le

# $ % & product

$ack titration ! titration in "hich a reagent is added to a


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$ack titration. ! titration in "hich a reagent is added to a

solution containing the analyte, and the e0cess reagent

remaining after its reaction "ith the analyte is determined

by a titration.

This titration is used, 'hen"

•

the titration reaction is too slo,,• a suitable indi#ator is not a(ailable,

• there is no useful dire#t titration reaction

•

the standard solution la#ks of stabilit) $fugitive% # $ % e(cess & product ) $ % residue

% residue $ % padding & product *


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displacement titration+ ! titration in "hich the analytedisplaces a species, usually from a comple0, and the amountof the displaced species is determined by a titration.

This titration is used, 'hen"

• the analytes are unstable substance

• 3t is impossible to indicate the e(uivalent $end% point in directreaction

• !nalyte doesn’t react "ith titrant• reaction involving the titrant and analyte mustn’t be of kno"n

stoichiometry, quantitatively


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# $ % ( padding compounds ) & #( substituent )

#( substituent ) $ % & product

4r4l7 I 9e4l K 4r4l I 9e4l7 analyte substitute

=9e4l7 I MnD; I H4l K =9e4l I 4l I Mn4l7 I ;H7D


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evertive titration.

• A standard solution is titrated b) solution of

in(estigated substan#e in re(ersi(e titration

#(in burette) $ % (in !lask) & product


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;. 4alculations in titrimetric analysis.

• eight of investigated substance by results of direct, displacement or

reversive titration:

a

k mT@A

31999

383B 4m

⋅

⋅

a

k T@AT

3

33B T

m

⋅


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• =eight of in(estigated substan#e b) results

of ba#k titration:

a

k mT@AT@A

31999

38!3B 43B 4m 2211


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• Titre of titrant b) in(estigated substan#e:

1999

!A8!TCD mE

7D

⋅

=

5 P?ITI;JTIM8T?J I? A%K +A8 T%T?AT%I6 A


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!cid&base titration # titration in "hich the reaction

bet"een the analyte and titrant is an acid&base reaction.

Protol)tometr) is titrimetric method of analysis "hich uses

solutions of acids or bases as titrants. 3n this method of the

analysis defined substances are the substances, capable to

react "ith acids and the bases.The basi# rea#tion of a method:

EF F GE* H E2G or

A F + H +F

F A*

5. P?ITI;JTIM8T?J I? A%K–+A8 T%T?AT%I6 A

68LT?A;%AT%I6 M8TIK!: T8 +A% I68PT"

T%T?A6T" K8N%68K L+TA68.


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Methods of acid#base titration or acid&base titrimetry:

• a#idimetr) titrants * l" 2I4!

• alkalimetr) titrants # 6aI" BI!

All titrants are se#ondar) standard solutions"

therefore demand of standardiOation

definition of pre#ise #on#entration!.


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/tandardi


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/tandardi


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/tandardi


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/tandardi


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/tandardi


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/tandardi


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/tandardi


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!ccording to force of acid and the base such

types of the acid#base interaction are possible:

et'een strong acid and the strong basis

-a./ $ /0l & / *. $ -a0l

et'een 'eak acid and the strong basis

-a./ $ 0/ 10../ 2 0/ 10..-a $ / *.

et'een strong acid and the 'eak basis

-/ 3./ $ /0l & -/ 30l $ / *.

et'een 'eak acid and the 'eak basis

0/ 10../ $ -/ 3./ & 0/ 10..-/ 3 $ / *.


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1CG; the ionic theory of indicators


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1CG; & the ionic theory of indicators

%ndi#ators of an a#id*base titration methodare ,eak a#ids or the bases at ,hi#h notionised mole#ules and ions ha(e different#olouring

%nd Q F F %nd*

;a#mus red blue

Phenol*

phthalein #olourless#olourless rose

%nd: * one*#olour $phenolphthalein %

* t,o*#olour $methyl orange , la#mus%


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;imitation of ioni# theor) of indi#ators :

• !scertaining of different colouring of acidic

and basic forms, but is not present an

e0planation of presence and colouring change.

• The structure and colouring are not connected.

• 4olouring change is ionic process but "hy it

often is long in timeO

Ad(antages of the ioni# theor): possibility of

(uantitative interpretation of results of change

of colouring.

The theory of chromophore & colouring of organic


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The theory of chromophore colouring of organic

compounds is connected "ith presence of a

chromophore groups at molecules of indicators :

Au


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olouring #hange is a #onseuen#e of isomeri#

transformation ,hi#h #hanges an indi#ator

stru#ture

The #olourless form The )ello, form

6O

I

IA

I

I

6*I*A


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-imitation of chromophore theory of indicators

•

Eoes not give an e0planation "hy tautomerictransformations and change of colouring of a

solution of indicators occurs at change PL a

solution.

• 4olouring changes instant, "here as intra#

molecular transformations generally long

processes is fre(uent.

• Eoes not give a (uantitative estimation of

connection of colouring change "ith change PL.


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The ionic# chromophore theory

• The acid#base indicators are "eak acids and the

bases, and the neutral molecule of the indicatorand its ionised form contain differentchromophore groups

#olourless )ello, )ello,

6

O

I

I

I

I

6*I* I

I

6*I*

F F


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The ionic# chromophore theory

1 2

E%nd9 Q %nd Q F F %nd*

the a#id the base

form form

form#ase

formacid

&

& p' p%

.

.lg−=

1pB pA ±


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D of most often used indi#ators in the a#id*base

titration:

Meth)l orange 4"9

• Meth)l red 5"5

• ;a#mus &"9

• Phenolphthalein R"9

• pT of the indi#ator is (alue of E at ,hi#h #olour

of the indi#ator sharpl) #hanges and stop to addtitrant there is end point of titration!


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9actors "hich influence the indicator indication.

•

!t increase tQ the temperature indicator becomesless sensitive to LI #ions for indicators#bases

• 6resence of organic solvent $alcohol, acetone%,albuminous molecules, salts changes PR of theindicator

• 3t is necessary to define titre a "orking solutionin the same conditions at "hich the test analysis

is conducted• it isn’t recommended to take a lot (uantity of

indicator

7 3ndicator choice calculation of errors of


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7. 3ndicator choice, calculation of errors of

titration in a method protolytometry.

%ndi#ator #hoi#e spend t,o methods:

• In rea#tion produ#ts

•In titration #ur(es


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Titration curve for 9"1 mol; h)dro#hlori# a#id b) 9"1mol; sodium h)dro


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Eependence of inflection points on concentration of

defined substance

$8,1 mol'- and 8,81 mol'-%

Eependence of inflection points


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on force of acid



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on force of acid

Titration curve for "eak acid $4H 4DDH% by


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Titration curve for "eak acid $4H4DDH% by

"eak base $@H;DH%


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Titration curve for H6D; by @aDH

9actors "hich influence on


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9actors "hich influence on

inflection points

• #onstants of a#id or base

• temperatura of solutions

• #on#entration of defined substan#es

• #on#entration of used titrants

4hoice of the indicator:The pT of indicator $interval of transition of colouring


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The pT of indicator $interval of transition of colouring

# pH range% should be in limit of inflection points on a

titration curve

4hoice of the indicator:The pT of indicator $interval of transition of colouring


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The pT of indicator $interval of transition of colouring

# pH range% should be in limit of inflection points on a

titration curve

Titration curve of 8.188 M H4l


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"ith 8.788 M @aDH

Titration curve of 8,1 S 4H4DDH


82/102

Titration curve of 8,1 S 4H4DDH

by 8,7 M @aDH

Titration curve of 8,1 S @H


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Titration curve of 8,1 S @H by 8,1 M H4l


84/102

Titration curve of "eak acid by "eak base

Titration curve for =8.88 m- of 8.188 M 4H4DDH


85/102

"ith 8.188 M @aDH sho"ing the range of pHs $or pT%

and volumes of titrant over "hich the indicators

bromothymol blue and phenolphthalein are e0pected tochange color.


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Titration curve of mi0


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Titration curve of mi0

acetic and malatic acids

Malati# a#id

S-H1"5919*4

A#eti# a#id

S-H1"&419*5

S1:S2U194

l i i id


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Titration curve of maleinic acid

Titration curve 8,1 S o0alic acid


89/102

Titration curve 8,1 S o0alic acid

by 8,1 S @aDH

Eeterminate the end point by potentiometric "ay


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Eeterminate the end#point by potentiometric "ay


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3ndicator’s error :

)dro


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Titration in ,ater solutions is limited b) fa#tors:

• %t is impossible to titrate for a mi0 of acids or the bases if constants of dissociation differ less, thanon four order

•

%t is impossible to titrate for a mi0 of strong and"eak acids $bases%

• %t is impossible to titrate very "eak acids $bases%

• %t is impossible to titrate separately for a mi0 ofacids $bases% "ith near constants of dissociation

• %t is impossible to define substances "hich areinsoluble in "ater.

4hoice of solvents:


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• The constant of autoprotolysis solvent should be

as small as possible• 9or titration of the ,eak bases should be to take

a solvent "ith the e0pressed progeni# properties

$the acid nature of solvent%

• 9or titration of ,eak a#ids should be to take a

solvent "ith e0pressed protophili# properties,

$the basis nature of solvent%

• Eielectric inductivity of solvent should be as it

is possible above

The "eak bases often are titrated in the acetic acid


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medium

$strengthening of force of the bases%

• Titrant: perchlorate acid lI4

• /tandardi


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@ona(ueous acid&base titration of "eak bases by

perchlorate acid

• %ndi#ators: #r)stal (iolet $violet & blue or

green%,

thymol dark blue $yello" & rose%.

The "eak acids often are titrated in the medium


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dimethyl formamide, ethylene diamine, butylamine,

pyridine

$strengthening of force of the acids%

• Titrant: sodium h)dro


98/102

/tandardi


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@ona(ueous acid&base titration of "eak

acids by @aDH or 4HD@a

• %ndi#ators: thymol blue $red#yello" and

yello"#blue% or physico#chemical methods$potentiometry%.

3n nona(ueous acid&base titration determinate


100/102

(

the end#point by potenthiometric "ay

3n nona(ueous acid&base titration determinate


101/102

the end#point by potenthiometric "ay


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Thanks !or your attention5

Documents

4.Titrimetric Analysis. Acid_Base Titration