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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
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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-
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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-
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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
Answer: In the equivalent point
Mol Na-EDTA = mol CaCO3
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
Answer: In the equivalent point
Mol Na-EDTA = mol CaCO3
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
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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
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 7,0 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
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V Na-EDTA = 7,1 x 10-3
L
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 7,1 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
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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
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
Known : V well water = 10 ml
V Na-EDTA = 7,0 x 10-3
L
Asked : hardness of well water
Answer : we use formula in eqivalent point
mol CaCO3 = Mol Na-EDTA
M x V = M x V
http://en.wikipedia.org/wiki/File:Erio_T.svg8/2/2019 complexiometry
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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
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 7,1 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
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=][
][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
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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
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L. AttachmentStandardization Na-EDTA with CaCO3 as primery standard
After titration Titrator
Istiana Yuli
Purwati
Nurhalimah
Romadhoni
Determining Hardness of Well Water
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PictureTitrator
Before Titration After Titration
Romadhoni
Istiana
Nurhalimah