A. TITLE

Acidi -Alkalimetry

B. DATE OF EXPERIMENT

Tuesday, 22nd November 2011, at 07.30 am

C. FINISH OF EXPERIMENT

Tuesday, 22nd November 2011, at 11.30 am

D. OBJECTIVES

1. Making and determine standarization of base solution.

2. Determine precentage of H2SO4 in accu zuur.

E. BASIC THEORY

Titration is a procedure used to determine the amount of reactant present in a

chemical solution; it is used to cause a reaction in such a way that the reactant is

not in excess.

The kinds of titration :

1. Acid base titration

2. Redox titration

3. Complex formation titration

4. Precipitation titration

Use an indicators in titration

This method relies on observing a color change in the solution. Indicators are

weak organic acids or bases that are different colors in their dissociated and

undissociated states. Because they are used in low concentrations, indicators do

not appreciably alter the equivalence point of a titration. The point at which the

indicator changes color is called the end point.

Table of Commen Acid-Basa Indicators

Indicator pH range Quantity per 10 mL Acid Base

Thymol Blue 1.2-2.8 1-2 drops 0.1% soln. in aq red yellow

Pentamethoxy red 1.2-2.3 1 drop 0.1% soln. in 70%

alc.

red-

violet

Colorles

s

Tropeolin OO 1.3-3.2 1 drop 1% aq. soln. red Yellow

2,4-Dinitrophenol 2.4-4.0 1-2 drops 0.1% soln. in

50% alc.

colorles

s

Yellow

Methyl yellow 2.9-4.0 1 1 drop 0.1% soln. in 90%

alc.

red Red

Methyl orange 3.1-4.4 1 drop 0.1% aq. soln. red

orange

red orange

Bromphenol blue 3.0-4.6 1 drop 0.1% aq. soln. yellow blue-

violet

Tetrabromphenol

blue

3.0-4.6 1 drop 0.1% aq. soln. yellow blue

p-Nitrophenol 5.0-7.0 1-5 drops 0.1% aq. soln. colorles

s

yellow

Azolitmin 5.0-8.0 5 drops 0.5% aq. soln. red yellow

Phenol red 6.4-8.0 1 drop 0.1% aq. soln. yellow red

Neutral red 6.8-8.0 1 drop 0.1% soln. in 70%

alc

red yellow

Rosolic acid 6.8-8.0 1 drop 0.1% soln. in 90%

alc

yellow red

Cresol red 7.2-8.8 1 drop 0.1% aq. soln. yellow red

α-

Naphtholphthalein

7.3-8.7 1-5 drops 0.1% soln. in

70% alc.

rose Green

Tropeolin OOO 7.6-8.9 1 drop 0.1% aq. soln. yellow rose-red

Thymol blue 8.0-9.6 1-5 drops 0.1% aq. soln. yellow Blue

Phenolphthalein 8.0-10.0 1-5 drops 0.1% soln. in

70% alc.

colorles

s

Red

α-Naphtholbenzein 9.0-11.0 1-5 drops 0.1% soln. in

90% alc.

yellow Blue

Thymolphthalein 9.4-10.6 1 drop 0.1% soln. in 90%

alc.

colorles

s

Blue

Nile blue 10.1-

11.1

1 drop 0.1% aq. soln. blue red

Alizarin yellow 10.0-

12.0

1 drop 0.1% aq. soln. yellow Lilac

Salicyl yellow 10.0-

12.0

1-5 drops 0.1% soln. in

90% alc.

yellow orange-

brown

Titrimetric analysis or volumetric analysis is a quantitative analysis by reaction

of a substance to be analyzed with standard solution (standard) which has been

accurately known concentration, and reaction between the substance being analyzed and

the standard solution took place quantitatively.

One of the main group in the classification of titrimetric analysis is the

neutralization reaction or acidimetry and alkalimetry. Alkalimetri acidi method used

to determine the concentration of acid or base number is not known. 

Acidimetry a titration technique with acid as titrant, while alkalimetry a titration

with a base as the titrant (Christian 1994). Experiment of acididi-alkalimetry aims is

to determine the concentration of acid or base titrat with previously standardized

base or acid used as titrat. Substances used in the titrimetric must have high

purity. So before use, reagent concentration and volume must be known precisely by

means of standardization (Harjadi 1986).

Standardization is the process by which the concentration of a solution is

accurately. The solution that can use for standardization process called primary

standard. Primary standard should have the following characteristics:

1. It should be readily available in a pure form or in state of known purity at a

reasonable cost. In general, the total amount of impurities should not exceed

0,01 to 0.02%, and it should be possible to test for impurities by qualitative

tests of known sensitivity.

2. The substance should be stable. It should be easy to dry and should not be so

hygroscopic that it takes up water during weighing. It should not lose weight

on exposure to air. Salt hydrates are not normally employed as primary

standards.

3. It is desirable that the primary standard have a reasonably high equivalent

weight in order to minimize the consequences of errors in weighing.

(Underwood )

The formula is

V1 x N1 = V2 x N2

Where:

V1 = Volume of penetration solution (ml)

N1 = Normality of penetration solution (gram equivalents / liter)

V2 = volume of titrated solution (ml)

N2 = Normality of titrated solution (gram equivalents / liter)

End Point titration indicated by the color change indicator, equivalent point

occurs at the trajectory (range) pH indicator. the stoichiometry, acid or hydrogen ions

and base hydroxide ions tepat habis bereaksi at the equivalence point.

H+ + OH- H2O

Acid equivalence = Base equivalence

Phenolphthalein and Methyl Orange Indicators

The well-known indicator phenolphthalein (below) is a diprotic acid and is

colorless. It dissociates first to a colorless form and then, on losing the second

proton, to an ion with a conjugated system; a red color result.

Methyl orange, another widely used indicator, is a base and is yellow in the

molecular form. Addition of a proton gives a cation which is pink in color.

Calculation of Percent Purity

To analyze a sample of unknown purity the analyst weighs accurately a portion

of the sample, dissolves it appropriately, and titrates it with a standard solution. If the

titration reaction is

aA + Tt product

Where a molecules of the analyte, A, react with t molecules of the titrant, T, then at

the equivalence point

t mmol A = a mmol T

mmol A = at

x mmol T

If V and M represent the volume (mL) and molarity (mmol/mL), respectively, of the

titrant, and MWA is the molecular weight of the analyte, then

mmol A = at

x V x M

mg A = at

x V x M x MWA

The precent by weight of A is

% A = mganalytemg sample

x 100

% A = atxV (mL ) x M (mmolmL

x)MW A(mg /mmol)

weight of sample (mg)x 100

F. CHEMICALS AND EQUIPMENT

Chemicals:

1. H2C2O4.2H20 : 0,6008 g

2. Accu Zuur

3. NaOH

4. Phenolphthalein indicators

5. Methyl orange

6. Aquadest

Equipment:

1. Volumetric Flask 100 mL

2. Erlenmeyer 100 mL

3. Graduated Cylinder 10 mL

4. Stative

5. Burette

6. Volumetric Pipette

7. Pipette

8. Spatula

9. Funnel

10. Beaker glass

G. PROCEDURE

Standardization NaOH Solution ± 0,1 N With Oxalate Acid as Primary

Standard.

0,6008 gram H2C2O4.2H2O

Pouring into volumetric flask 100 mlDisolving with aquades and dilute untile boundariesShaking well

Standard solution

Indicator change color

Pipettte 10 mlPouring into conical flaskAdding 25 ml aquadesAdding 3 drops of PP indicatorTitrate with NaOH solution Stop when the changes of indicators colorRead and write the number at initial and end titrationDetermining volume NaOHRepeating until 3 times with the same volume of H2C2O4.2H2OCalculate average concentration of NaOH solution

Determining percentage of H2SO4 in accu zuur

2 ml accu zuur

Dencity of accu zuur

Pouring into piknometer with volumetric pipette 2 mlClose the piknometer soonWeight again piknometer + accu zuur

100 ml aquadest in volumetric flask

Indicator change color

Pouring accu zuur with the funnel Rinse the remnant Dilute until boundariesLet 1-2 our until reach the room temperaturePippete 10 ml solutionPouring into conical flaskAdding drops of metil orange indicatorTitrate with NaOH 0,1 M until there is color changeRepeating until 3 times and calculate amount of H2SO4 in accu zuur

H. EXPERIMENT DATA

Standardization NaOH Solution ± 0,1 N With Oxalate Acid as Basic Solution.

NoScale Volume

NaOH (ml)N NaOH

(eq/L)Titrator

Initial (mL) End (mL)1. 0 8,8 8,8 O,1084 Romadhoni

2. 8,8 17,8 9 0,1060 Nurhalimah

3. 17,9 26,9 9 O,1060 Istiana

Detemining percentage of H2SO4 in accu zuur

NoScale Volume

NaOH (ml)% H2SO4 Titrator

Initial (mL) End (mL)1. 33,3 49,3 16 63,90 Nuurhalimah 2. 31,2 48,9 17,7 70,53 Istiana 3. 16 30,8 14,8 58,99 Romadhoni

I. ANALYSIS

Standardization NaOH Solution ± 0,1 N With Oxalate Acid as Primary

Standard.

Before doing titration Washing burette with NaOH solution in order to make

NaOH concentration is not changed by a drop of water that left.

H2C2O4.2H2O solution is used as the primary standard solution because this

solution is not hygroscopic, so it takes up water during weighing. And it has high

equivalent weight, so minimize the consequences of error in weighing.

In the standardization of NaOH solution, the addition of phenolphthalein

indicators that serve to know the equivalent point titration. Phenolphthalein indicator

is used because this standardization is a weak acid titration (H2C2O4.2H2O) and

strong base (NaOH) so the equivalent point above 7 and in trajectory indicator of

phenolphthalein is 8.0 to 9.6.

Phenolphthalein indicator classified as weak acid, in condition not ionized this

indicator is colorless. So when phenolphthalein indicator was added in H2C2O4.2H2O

solution, there is no changes color. Phenolphthalein indicator in base condition

given light color because of the anion.

The reaction is:

H2C2O4.2H2O (aq) + 2 NaOH (aq) Na2C2O4 (aq) + 4 H2O (l)

In our experiment we get the normality of NaOH when the volume 8,8 mL is

O,1084 eq/L.

Calculation:

m H2C2O4.2H2O = 0,6008 gram

V = 0,1 L

N = 0,6008gram

63gram /eq .0,1L

N = 0,0954 eq/L

V NaOH x N NaOH = V H2C2O4.2H2O x N H2C2O4.2H2O

0,0088 L x N NaOH = 0,01 L x 0,0954 eq/L

N NaOH = 0,1084 eq/L

The normality of NaOH when the volume 9,0 mL is 0,1060 eq/L.

V NaOH x N NaOH = V H2C2O4.2H2O x N H2C2O4.2H2O

0,009 L x N NaOH = 0,01 L x 0,0954 eq/L

N NaOH = 0,1060 eq/L

The normality of NaOH when the volume 9,0 mL is 0,1060 eq/L.

V NaOH x N NaOH = V H2C2O4.2H2O x N H2C2O4.2H2O

0,009 L x N NaOH = 0,01 L x 0,0954 eq/L

N NaOH = 0,1060 eq/L

So the averege normality of NaOH is

Average N NaOH = 0,1084N+0,1060N+0,1060N

3

= 0,1068 eq/L

Determining percentage of H2SO4 in accu zuur

Determining H2SO4 solution in the accu zuur, addition of methyl orange

indicator is to determines the equivalent point in the titration. Methyl orange is used

because for titration H2SO4 with NaOH has a pH below 7 at the equivalent point and

in trajectory methyl orange indicator is 3.1 to 4.4. Methyl orange is the sodium salt

of a sulphonic acid. Anion in alkaline environment gives a yellow color. While in

acid condition methyl orange is a weak base and containing H+ ions, there is a

changes in the structure and gives the red color of the ions.

The reaction is:

H2SO4 (aq) + NaOH (aq) Na2SO4 (aq) + H2O (l)

The mass of sample of H2SO4 is

Dencity = massVolume

= 87,5485g−21,8904 g

50ml

= 1,3132 g/mL

mass of sample = 2 mL x 1,3132 g/mL = 2,6264 g

The percentage H2SO4 when volume of NaOH 16 mL is 63,90%.

V H2SO4 x N H2SO4 = V NaOH x N NaOH

0,01 L x N H2SO4 = 0,016 L x 0,1068 eq/L

N H2SO4 = 0,1709 eq/L

In 100 ml = 2 x 100 x 0,1709

= 34,18 mmol

mmol = mgBM

mg = 34,18 x 49

= 1674,82 = 1,6748 g

% H2SO4 = 1,6748g2,6264 g

x 100

= 63,90 %

The percentage H2SO4 when volume of NaOH 17,7 mL is 70,53 %.

V H2SO4 x N H2SO4 = V NaOH x N NaOH

0,01 L x N H2SO4 = 0,0177 L x 0,1068 eq/L

N H2SO4 = 0,1890 eq/L

In 100 ml = 2 x 100 x 0,1890 N

= 37,80 mmol

mmol = mgBM

mg = 37,80

= 1852,2 = 1,8522 g

% H2SO4 = 1,8522g2,6264 g

x 100

= 70,53 %

The percentage H2SO4 when volume of NaOH 14,8 mL is 58,99 %.

V H2SO4 x N H2SO4 = V NaOH x N NaOH

0,01 L x N H2SO4 = 0,0148 L x 0,1068 eq/L

N H2SO4 = 0,1581 eq/L

In 100 ml = 2 x 100 x 0,1581 N

= 31,62 mmol

mmol = mgBM

mg = 31,62

= 1549,38 = 1,5494 g

% H2SO4 = 1,5494 g2,6264 g

x 100

= 58,99 %

So the averege percentage of H2SO4 is

Average % H2SO4 = 63,90+70,53+58,99

3

= 64,47 %

The percentage of H2SO4 in accu zuur is 64,47%, but we don’t know the percentage

of H2SO4 certain. Because in our accu zuur that we use there is no label of

compotition of accu zuur.

J. DISCUSSION

Application: Determining percentage of H2SO4 in Accu Zuur

In the determining percentage of H2SO4 there is a factor that influence the data

experiment:

There are differences between volume of NaOH that use. In the first experiment

we need NaOH 16 mL. In the second experiment we need NaOH 17,7 mL and in

the third experiment, we need NaOH 14,8 mL. It caused by in the second

experiment, when we add NaOH solution in the analyte the volume is pass the

equivalent point. In the first and second experiment we use NaOH in the bottle 2,

but when we want to continue in the last titration, NaOH solution in bottle 2 is

fresh out. So in a pinch we use NaOH solution in the bottle 3.

K. CONCLUSION

Based on our experiment normality average NaOH solution is 0,1068 eq/L

Based on our experiment percentage of H2SO4 in accu zuur is 64,47%

L. ANSWER OF QUESTION

1. Why in the manufacture of NaOH solution had to use hot water?

Answer:

The aim that have been boiling the water used is to avoid an explosion, because

the reaction of alkali metal (Na) is exothermic and alkali metals are also easily

react with water.

2. What's the difference between:

Answer:

a. Standard solution and primary solution?

Primary solution: where the solution concentration is known from the results

of the weighing and dilution, the concentration is determined from the

calculation

Standard solution: where the solution concentration was determined with

accuracy.

b. Acidimetry and alkalimetri

Acidimetry is a neutralization titration technique with acid as titrant.

Alkalimetri is a neutralization titration with a base as the titrant.

3. Give reasons for the use of indicators in the titration of the above!

Answer:

Phenolphthalein indicator is used because this standardization is a weak acid

titration (H2C2O4.2H2O) and strong base (NaOH) so the equivalent point above 7

and in trajectory indicator of phenolphthalein is 8.0 to 9.6.

Methyl orange is used because for titration H2SO4 with NaOH has a pH below 7 at

the equivalent point and in trajectory methyl orange indicator is 3.1 to 4.4.

4. 1.2 grams NaOH and Na2CO3 dissolve in sample and titrated with 0.5 N HCl

with indicator pp. After addition of 30 mL of HCl solution became

colorless. Then methyl orange indicator was added and titrated again with

HCl. After addition of 5 mL of HCl solution became colorless. How much the

percentage of Na2CO3 and NaOH in the sample?

Answer:

Known :

Mass of NaOH : 1,2 grams

Mass of Na2Co3 : 1,2 grams

N of HCl : 0,5 N

V1 HCl : 30 mL

V2 HCl : 5 mL

Asked :

% Na2CO3…?

% NaOH…?

Solution

% Na2CO3

N Na2CO3 =

mgNa2CO 3

BENa2CO 3 .Volx 1

=

1200mg842x10

= 2,8 N

Equivalence of Na2CO3 = Equivalence HCl

Equivalence of Na2CO3 = NHCl x VHCl

= 2,8 N x 60 mL

= 168 miliequivalence

gram Na2CO3= equivalence x Equivalence Weight x 10

= 168 x 84 / 2 x 10

= 70560 mg

Ratio of Na2CO3 =

70560

1,2x 103100 %

= 58,8

%NaOH :

NNaOH =

mgNaOHBENaOH .Vol

x 1=

1200mg401x10

= 3 N

Equivalence NaOH = Equivalence HCl

Equivalence NaOH = N x V

= 3 N x 60 mL

= 180 miliequivalence

gram NaOH = Equivalence x equivalence Weight x 10

= 180 x 40 / 1 x 10

= 72000 mg

Ratio NaOH =

72000

1,2x 103100 %

= 60 %

4. At which pH can color changes of pp indicators?

At Ph of 8,0-9,6

M. REFERENCES

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.

http://chemistry.about.com/od/acidsbases/a/aa082304a.htm.Access at 25nd

November 2011, at 06.30 pm

http://chemistry.about.com/od/acidsbases/a/Acid-Base-Indicators.htm.Access at

25nd November 2011, at 06.30 pm

ATTACHMENT

Picture

TitaratorBefore titration After Titration

H2C2O4.2H2O + Phenolphthalein Indicator

Result experiment 1NaOH + H2C2O4.2H2O + Phenolphthalein Indicator

Rhomadhoni

Result experiment 2NaOH + H2C2O4.2H2O + Phenolphthalein Indicator

Nurhalimah

Result experiment 3NaOH + H2C2O4.2H2O + Phenolphthalein Indicator

Istiana Yuli Purwati

Standardization NaOH Solution ± 0,1 N With Oxalate Acid as Primary Standard

Picture

TitaratorBefore titration After Titration

H2SO4 + Methyl Orange Indicator

Result experiment 1H2SO4 + Methyl Orange

Indicator + NaOH

Nurhalima h

Result experiment 2H2SO4 + Methyl Orange

Indicator + NaOH

Istiana Yuli Purwati

Result experiment 3H2SO4 + Methyl Orange

Indicator + NaOH

Rhomadhoni

Determining Percentage of H2SO4 in Accu Zuur