complexiometry

8/2/2019 complexiometry

1/19

A. TitleComplexiometry Titration

B. Date of ExperimentStart : 20 Desember 2011,at 8.00 AM

Finish : 20 Desember 2011, at 11.30 AM

C. Objectivesa. Standardization of Na-EDTA solution with CaCO3 as primery standardb. Determine hardness of well water

D. Basic TheoryOne way of determining levels of metal ions on the formation of a complex

compound between the metal ion complex-forming compounds is by complexiometric

titration. Complex-forming compounds as electron donors whereas metal ions that act

as electron acceptors. In alkaline solution, complex formation is more efficient and

more stable. However, if too alkaline, should really pay attention to the formation of

oxidized metal deposition.

Complexiometric Titration namely titration based on the formation of complex

compounds (ion complex or salt that are hard to ionizes), Complexiometric is a type

of titration in which the titrant and analyte complexed each other, forming a complex

result. The reactions of complex formation or which involves many complex and its

application are also many, not only in the titration. Because it needs a fairly broad

understanding of the complex, although here it will first be applied on titrations.

Basic requirements in complexiometric titration is neutral complex formation

molecule that dissociates in solution is the solubility of high-level, such as metal

complexes with EDTA.

One type of chemical reaction that serves as a basis for determining titrimetricinvolves the formation (formation) complex or complex ion which dissolves but

slightly dissociated. The complex is referred to here is the complex formed by

reaction of metal ions, a cation, with an anion or neutral molecule.

Titration complexiometric also known as reaction formation reaction involves

complex ions or the formation of a neutral molecule that dissociates in solution. Such

complex formation is a fundamental requirement is a high level of solubility. In

addition to ordinary complex titration as above, also known complexiometric, as it

involves the use of EDTA.


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EDTA is potentially a sexidente ligand which may coordinate with a metal ion

through its two nitrogens and four carboxyl groups. EDTA or

ethylenediaminetetraacetic acid is a novel molecule for complexing metal ions. It is a

polyprotic acid containing four carboxylic acid groups (acidic hydrogens are red) and

two amine groups with lone pair electrons (green dots). The classic structural formula

is given below. EDTA is synthesized on an industrial scale from ethylenediamine,

formaldehyde, and a source of cyanide (HCN or NaCN. The structure of EDTA :

Ethylene diamine tetra acetic acid or more commonly known as EDTA, is one

type of amine polycarboxylic acid. EDTA is actually seksidentat ligand that can

coordinate with a metal ion through both nitrogen and fourth of his or carboxyl group

called multidentat ligands containing more than two coordination atoms per molecule,

such as 1,2-diaminoetanatetraasetat acid (asametilenadiamina tetraasetat, EDTA)

which has two nitrogen atoms - contributor and four oxygen donor atoms in a

molecule.

For more convenience, free acid form of EDTA (Ethylene Diamine Tetra

Acetic Acid) is often abbreviated H4Y. But that is often used is the sodium salt

(Na2H2Y). The solution is quite acidic, partly protonisasi EDTA without total

disintegration of metal complexes can occur, leading to species such as CuHY-, but in

general the condition that the four hydrogen disappeared armpit ligand coordinatedwith a metal ion. At a very high pH values, hydroxide ions can penetrate the layer of

metal coordination, and complexes such as Cu (OH) Y3-

can arise.

For a variety of metal ions and chelating Bahn like EDTA, the value of

equilibrium constant for these reactions can be formulated as follows:

Mn+ + Y4-

MY-(4-n)

Kabs =

Kabs-called absolute stability constant or formation constant absolute.


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Complex formation between metal ions with EDTA depends on the pH of the

solution. At pH values greater majority EDTA was present as tetraanion Y4-

. At lower

pH values, species-that terprotonisasi HY3 etc, become dominant. It can be seen that

the H3O+

compete with metal ions to EDTA, and it is clear that a real tendency to

form a brown metal at any pH value can not be seen directly from Kabs.

Titration can be determined by the addition of a useful indicator as a sign of

the titration endpoint is reached. There are five conditions of a metal ion indicator can

be used in the visual detection of the end points of the color reaction should be such

that before the end point, when almost all metal ions have been berkompleks with

EDTA, the solution will be a strong color. Second, it must be specific color reactions

(specific), or at least selectively. Third, the metal-indicator complex should have a

fairly stable, if not, because of dissociation, will not obtain a sharp color change.

However, the metal-indicator complex should be less stable than the metal-EDTA

complexes to ensure that the end point, EDTA remove metal ions from metal-

indicator complex to the metal-EDTA complex must be sharp and quick. Fifth, the

color contrast between free and complex indicators-indicators of metal should be such

so easily observed. Indicators need to be very sensitive to metal ions, so that the color

change occurs as little as possible with the equivalent point.

Finally, the determination of Ca and Mg can be performed by EDTA titration,

pH for the titration was 10 with the indicator Eriochrome Black T (EBT). At high pH

12, Mg (OH)2 will precipitate, so that EDTA can be consumed only by Ca2+

with the

indicator murexide.

Hard water is water that has high mineral content (in contrast with "soft

water"). Hard water is generally not harmful to one's health, but can pose serious

problems in industrial settings, where water hardness is monitored to avoid costly

breakdowns in boilers, cooling towers, and other equipment that handles water. In

domestic settings, hard water is often indicated by a lack of suds formation when soap

is agitated in water. Wherever water hardness is a concern, water softening is

commonly used to reduce hard water's adverse effects.

Water's hardness is determined by the concentration of multivalent cations in

the water. Multivalent cations are cations (positively charged metal complexes) with a

charge greater than1+

. Usually, the cations have the charge of2+

. Common cations

found in hard water include Ca2+

and Mg2+

. These ions enter a water supply by

leaching from minerals within an aquifer. Common calcium-containing minerals are


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calcite and gypsum. A common magnesium mineral is dolomite (which also contains

calcium). Rainwater and distilled water are soft, because they also contain few ions.

The following equilibrium reaction describes the dissolving/formation of

calcium carbonate scales:

CaCO3 + CO2 + H2O Ca2+

+ 2HCO3-

Calcium and magnesium ions can sometimes be removed by water softeners.

Temporary hardness is a type of water hardness caused by the presence of

dissolved carbonate minerals (calcium carbonate and magnesium carbonate). When

dissolved, these minerals yield calcium and magnesium cations (Ca2+

, Mg2+

) and

carbonate and bicarbonate anions (CO32-

, HCO3-). The presence of the metal cations

makes the water hard. However, unlike the permanent hardness caused by sulfate and

chloride compounds, this "temporary" hardness can be reduced either by boiling the

water, or by the addition of lime (calcium hydroxide) through the process of lime

softening. Boiling promotes the formation of carbonate from the bicarbonate and

precipitates calcium carbonate out of solution, leaving water that is softer upon

cooling.Permanent hardness is hardness (mineral content) that cannot be removed by

boiling. When this is boiling the case, it is usually caused by the presence of calcium

and magnesium sulphates and/or chlorides in the water, which become more soluble

as the temperature rises. Despite the name, the hardness of the water can be easily

removed using a water softener, or ion exchange column.

Hardness can be quantified by instrumental analysis. The total water hardness,

including both Ca2+

and Mg2+

ions, is reported in parts per million (ppm) or

mass/volume (mg/L) of calcium carbonate (CaCO3) in the water. Although water

hardness usually measures only the total concentrations of calcium and magnesium

(the two most prevalent divalent metal ions), iron, aluminium, and manganese can

also be present at elevated levels in some locations. The presence of iron

characteristically confers a brownish (rust-like) colour to the calcification, instead of

white (the color of most of the other compounds).

Because it is the precise mixture of minerals dissolved in the water, together

with the water's pH and temperature, that determines the behavior of the hardness, a

single-number scale does not adequately describe hardness. Descriptions of hardness

correspond roughly with ranges of mineral concentrations:

Soft : 060 mg/L


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Moderately hard : 61120 mg/L

Hard : 121180 mg/L

Very hard : 181 mg/L

The level of total hardness in water can be evaluated with commercial testing

kits, which measure the concentrations of calcium and magnesium. Several scales are

used to describe the hardness of water in different contexts. The hardness is indicated

by a calculation where both calcium and magnesium values are reported as mg/L

(ppm) (Ca x 2.5) + (Mg x 4.12)= Hardness in mg/L

E. Chemicals and Equipments CaCO3

Aquadest HCL 6M Na-EDTA Buffer Solution PH 10 BET Indicator Volumetric Flask 100 mL Conical flask 100 mL

Graduated Cylinder 10 mL Burette Volumetric Pipette Pipette Mineral water


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F. ProcedureStandardization of Na-EDTA with CaCO3 as primery standard

CaCO3 as primery standardnCaCO3

Pipette 10 ml into conical flask

Adding 5 ml buffer solution with pH 10

Adding 3 drops of EBT indicators

Titrating with Na-EDTA 0,01 M

Stop when there is changes color from red

wine become blue

Calculate concentration of Na-EDTA

solution

Moving to the volumetric flask 100 mL

Adding aquadest 100 mL

Adding HCl 1:1 drops by drops until

bubbles gas lose

Diluting until limit sign

Shaking well

0,0804 grams of CaCO3

Ca2+

+ Y4-

CaY2-

nCaCO3


7/19

Determining hardness of well Water

G. Experimental DataStandardization of Na-EDTA with CaCO3 as primery standard

10 ml well water

Pipette into conical flask

Adding 2 ml buffer pH 10

Adding 3 drops of EBT indicators

Titrate wit Na-EDTA standard untillimit sign

Calculate hardness of CaCO3/ liter

Ca2+

+ Y4-

CaY2-

nCaCO3


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No ProcedureExperiment

Result

Hypothesis

/ ReactionConclusion

1o CaCO3 =

white

o CaCO3 +H2O = turbid

solution

o CaCO3 +H2O + HCl

= colorless

o CaCl2 +Buffer

solution =

colorless

o CaCl2 +Buffer

solution +

EBT

indicator =

pink

o Titrated withNa-EDTA=

pink become

blue

o V1Na-EDTA= 7,3 ml

o V2 Na-EDTA = 7,4

ml

o V3 Na-EDTA = 7,4

ml

oBeforetitrated

CaCO3(s) + 2

HCl(aq)

CaCl2(aq) +

H2O(l)+ CO2

(g)

oSample: redwine

oAfter titratedwith Na-

EDTA

Ca2+

+ Y4-

CaY2-

M of Na-

EDTA is

0,0108

CaCO3 as primery standard

Pipette 10 ml into

conical flask

Adding 5 ml

buffer solution

with pH 10

Adding 3 drops of

EBT indicators

Titrating with Na-

EDTA 0,01 M

Stop when there is

changes colorfrom red wine

become blue

Calculate

concentration of

Na-EDTA

Moving to the

volumetric

flask 100 mL

Adding

aquadest 100

mL

Adding HCl 1:1

drops by dropsuntil bubbles

gas lose

Diluting until

limit sign

Shaking well

0,0804 grams of CaCO3

Ca2+

+ Y4-

CaY2-


9/19

Determining Hardness of Well Water

No ProcedureExperiment

Result

Hypothesis/

Reaction

Conclusion

1 V1= 7,3 ml

V2 = 7,0 ml

V3 = 7,1 ml

Well water

colorless

Buffer

solution

colorless

Well water +

buffer + EBT

red wine

After titrated

with Na-

EDTA blue

solution

Ca2+

+ Y4-

CaY2-

Hardness of

well water

is 776,667

ppm

Well water

from

Widang

(Tuban)

H. Analysis and DiscussionAnalysis

a. Standardization Na-EDTA 0,01 M with CaCO3 as primery standard solutionIn our experiment, we use 0,0804 gram of CaCO3 then we poured into volumetric

flask, then we add aquadest. The reaction that occur is : CaCO3(s) + H2O(l)

CaCO3(aq) . After that we add HCl 1:1 drops by drops until the bubbles lose (CO2

lose). And then we dilute with aquadest again until formed CaCl2 solution. The

reaction that occur in this step is :

CaCO3(s) + 2 HCl(aq) CaCl2(aq) + CO2(g) + H2O(l)

10 ml well water

Pipette into

conical flask

Adding 2 ml

buffer pH 10

Adding 3 drops ofEBT indicators

Titrate wit Na-

EDTA standard

until limit sign

Calculate hardness

of CaCO3/ liter in

well water

Ca2+ + Y4-CaY2-


10/19

To know that CO2 is lose we observe with there is changes from turbid become

pure solution. After that we pipette 10 ml of CaCl2 solution 5ml of buffer

solution. And we add 3 drops of EBT indicators. In the basic, this titration formed

complex ions, Ca2+

with EDTA. The metals will form complex with EDTA in

different pH. Ca2+

react well in pH between 8 until 10.Forming of complex

between metallic ions with EDTA depends on pH solution. In this titration we use

EBT (Erichrome Black T). This indicator is include weak acid that have base 3

(H3In). Balancing of disotiation indicator will give different color and form

complex 1:1 with amount of metallic ions, so it will give different color in the end

of titration. The changes color in the titration is solution that contain metallic ions

of Ca2+

after adding EBT is become red wine. Then after in the eqivalent point,

between metallic ions of Ca2+

with EDTA can we observe from solution become

blue and indicators in the form of HIn2-

. The reaction in EBT indicator :

H2In- Hin

2-+ H

+

Red blue

With metallic ion: Ca2+

so it become

Ca2+

+ Hin2-

CaIn-+ H

+

Red wine

With EDTA : CaIn- + H2Y2- CaH2Y

2- CaH2Y + In3-

Red Wine

In3-

+ H2O HIn-+ OH

-

Blue

Then the solution titrated with Na-EDTA. We stopped where there is changes of

color from red wine become blue. The reaction that occur is : Ca2+

+ Y4- CaY

2-

The blue color that occur due to titrant is a mixture of MgY2-

and Y4-

. When

the mixture was added to a solution containing Ca2+, CaY2- the more stable will

be formed by free Mg2+

to react with the indicator (EBT) and form MgIn-red.

After the calcium is used in full, additional titrant change MgIn-

and

MgY2 indicator turns into a blue HIn2-

form. In this experiment we need Na-

EDTA 7,3 ml, 7,4 ml, and 7,4 ml.Then we calculate molarity of Na-EDTA by

using formula mol Na-EDTA = mol CaCO3. The molarity of Na-EDTA that we

get is 0,0110 M, 0,0108 M, 0,0108 M.

Calculation :

1. Known : mass of CaCO3 = 0,0804 V Na-EDTA = 7,3x 10-3 L


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Asked : M of Na-EDTA

Answer: In the equivalent point

Mol Na-EDTA = mol CaCO3

M x V = M x V

M x 7,3 x 10-3

L =

x 0,01 L

M = 0,0110

2. Known : mass of CaCO3 = 0,0804 V Na-EDTA = 7,4x 10-3 LAsked : M of Na-EDTA



M x V = M x V

M x 7,4 x 10-3

L =

x 0,01 L

M = 0,0108

3. Known : mass of CaCO3 = 0,0804 V Na-EDTA = 7,4x 10-3 LAsked : M of Na-EDTA



M x V = M x V

M x 7,4 x 10-3

L =

x 0,01 L

M = 0,0108

So the average Molarity of Na-EDTA is :

=

= 0,0108 M

b. Determine hardness of well waterIn here we use well water from Widang Tuban Jawa Timur, then we add 10mL,

then we add 2 ml of buffere solution. The purpose of addition buffer solution is

same with above experiment. And we use EBT indicator is also same with the

reason above. The sample of our group is use the well water is from Widang,

Tuban Jawa Timur.

The calculation :

1. Known : V well water = 10 mlV Na-EDTA = 7,3 x 10

-3L


12/19

Asked : hardness of well water

Answer : we use formula in eqivalent point

mol CaCO3 = Mol Na-EDTA

M x V = M x V

M x 0,01 L = 0,0108 M x 7,3 x 10-3

L

M = 0, 0079

n = M x V

= 0,0079 x 0,01 L

= 7,9 x 10-5

mol

m = n x Mr

= 7,9 x 10-5

mol x 100,09

= 0,0080 g

= 8,0000 mg

Hardness =

= 800 ppm

2. Known : V well water = 10 mlV Na-EDTA = 7,0 x 10

-3L




M x V = M x V

M x 0,01 L = 0,0108 M x 7,0 x 10-3

L

M = 0, 0076

n = M x V

= 0,0076 x 0,01 L

= 7,6 x 10-5

mol

m = n x Mr

= 7,6 x 10-5

mol x 100,09

= 0,0076 g

= 7,6 mg

Hardness =

= 760 ppm

3. Known : V well water = 10 ml


13/19

V Na-EDTA = 7,1 x 10-3

L




M x V = M x V

M x 0,01 L = 0,0108 M x 7,1 x 10-3

L

M = 0, 0077

n = M x V

= 0,0077 x 0,01 L

= 7,7 x 10-5

mol

m = n x Mr

= 7,7 x 10-5

mol x 100,09

= 0,0077 g

= 7,7 mg

Hardness =

= 770 ppm

Average of Well Water Hardness =

= 776,6667 ppm

So from our calculation we know that well water from Widang (Tuban) is

very hardness. Because in Tuban there is lime mountain, and it can cause

the hardness become too high.

Discussion

In our experiment, there are no mistake and our result is appropriate with the

theory.

I. Conclusiono Molarity of Na-EDTA is 0,0108 Mo Hardness of well water is 776,667 ppm

J. Question Answer1. Complexiometric Titration

Chemical Formula of Na-EDTA


14/19

Molecular formula of Na-EDTA (HO2CCH2)2NCH2CH2N(CH2CO2H)2

Structure of EBT indicator

Its chemical formula can be written as HOC10H6N=NC10H4(OH)(NO2)SO3Na.

2. Solution cencentration CaCl2 by ppmKnown : V well water = 10 ml

V Na-EDTA = 7,3 x 10-3

L




M x V = M x V

M x 0,01 L = 0,0108 M x 7,3 x 10-3

L

M = 0, 0079

n = M x V

= 0,0079 x 0,01 L

= 7,9 x 10-5

mol

m = n x Mr

= 7,9 x 10-5

mol x 100,09

= 0,0080 g

= 8,0000 mg

Hardness =

= 800 ppm

Known : V well water = 10 ml

V Na-EDTA = 7,0 x 10-3

L




M x V = M x V
http://en.wikipedia.org/wiki/File:Erio_T.svg


15/19

M x 0,01 L = 0,0108 M x 7,0 x 10-3

L

M = 0, 0076

n = M x V

= 0,0076 x 0,01 L

= 7,6 x 10-5

mol

m = n x Mr

= 7,6 x 10-5

mol x 100,09

= 0,0076 g

= 7,6 mg

Hardness =

= 760 ppmKnown : V well water = 10 ml

V Na-EDTA = 7,1 x 10-3

L




M x V = M x V

M x 0,01 L = 0,0108 M x 7,1 x 10-3

L

M = 0, 0077

n = M x V

= 0,0077 x 0,01 L

= 7,7 x 10-5

mol

m = n x Mr

= 7,7 x 10-5

mol x 100,09

= 0,0077 g

= 7,7 mg

Hardness =

= 770 ppm

3. NH4OH + NH4Cl buffer[OH

-] =

][

][

Salt

Basekb

=][

][4

4

NH

OHNHkb


16/19

=][

][108,1

4

4

5

NH

OHNHxx

pH = 14pOH

10 = 14pOHpOH = 4

pOH = - log [OH-]

4 = - log [OH-]

[OH-] = 10

-4

10-4

=][

][108,1

4

4

5

NH

OHNHxx

][

][

4

4

NH

OHNH=

4

5

10

108,1

x

][4OHNH =

Vassmolecularm

mass

.

1,8 x 10-5

=V

mass

.35

6,3 x 10-4

. V = gr

eq VNH4OH = 1 L

so mass = 6,3 x 10-4

gram

][4OHNH =

Vassmolecularm

mass

.

][ 4NH =Vassmolecularm

mass

.

4. Since the perfection of the reaction depends on the pH titration titrant, the higherthe pH the better, so that the required buffer solution.

5. Known : VEDTA 1= 15,28 mL (V1V2) EDTA = 15,28-10,43MEDTA = 0,01016 M = 4,85 mL

VEDTA 2= 10,43 mL

Question : ppm CaCO3 dan ppm MgCO3 ?

Answer :

ppm CaCO3


17/19

mmol CaCO3 = mmol EDTA

= ( M x V ) EDTA

= 0,01016 x 10,43

= 0,1059 mmol

mg CaCO3 = mmol x Mr

= 0,1059 x 100

= 10,59 mg

ppm CaCO3 =L

mg

1,0

59,10

= 105,9 mg/L

ppm MgCO3mmol MgCO3 = mmol EDTA

= [ M x (V1V2)] EDTA

= 0,01016 x 4,85

= 0,0493 mmol

mg MgCO3 = mmol x Mr

= 0,0493 x 84

= 4,1412 mg

ppm MgCO3 =L

mg

1,0

1412,4

= 41,412 mg/L

K. ReferencesEriochrome Black T - Wikipedia, the free encyclopedia.html

Day,R.A.,Underwood,A.L.(1991).Quantitative Analysis (Sixth ed).New York:

Prentice Hall.

Tim Penyusun.(2011).Panduan Praktikum Kimia Analitik 1 Dasar-dasar Kimia

Analitik.Surabaya:Jurusan Kimia FMIPA UNESA.

Titrasi Pengomplekan Meilina Rizky Hadiyanti.html

Rehma Standardisasi Larutan Na-EDTA 0,01 M dengan CaCl2 Sebagai Baku dan

Aplikasinya dalam Penentuan Kadar Kesadahan Air Laut..html


18/19

L. AttachmentStandardization Na-EDTA with CaCO3 as primery standard

After titration Titrator

Istiana Yuli

Purwati

Nurhalimah

Romadhoni

Determining Hardness of Well Water


19/19

PictureTitrator

Before Titration After Titration

Romadhoni

Istiana

Nurhalimah

complexiometry

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