lembar pengesahan ICP

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A. TITLE OF EXPERIMENT *Titrimetry*

B. OBJECTIVE OF EXPERIMENT

1. Students can understand the standardization of HCl solution.

2. Students can understand the determination of carbonate and bicarbonate mixture.

C. LITERATURE REVIEW

The term ‘titrimetric analysis ‘ refers to quantitative chemical analysis carried out by determining the volume of a solution of accurately known concentration which is required to react quantitatively with a measured volume of a solution of the substance to be determinate. The solution of accurately known strength is called the standard solution. The weight of the substance to know be determined is calculated from the volume of the standard solution used and the chemical equation and relative molecular masses of the reading compounds (vogel, 1989: 257).

In order to obtain accurate quantitative data for a reaction in solution, it is necessary that the reaction be fast, complete and occur in fixed, reproducible amounts. The requirement for fast reaction is achieved readily when ionic species are involving, although in some other cases, it is necessary to warm the solution or add a catalyst. The reaction will be complete provided the equilibrium constant is large. The technique of volumetric analysis is the simple type of titrimetry, and involves the addition of controlled volumes of a reagent solution the titrant, to a known volume of another solution, the titrand in a volumetric titration. This procedure may be automated, and the changes detected instrumentally. In some cases, excess of a reagent is added and the axcess measured by back titration ( kealey, 2005 : 80)

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these involving gases. In titrametric analysis the reagent of known concentration is called the titrant and the substance being titrated is called the titrand. The alternative name has nt been extended to apparatus used in the various operations; so the term volumetric glassware and volumetric flasks are still common, but it is better to employ the expressions graduated glassware and graduated flasks and these are used throughout this book (vogel, 1989 : 257)

For a titration to be accurate we must add a stoichiometrically equivalent amount of titrant to a solution containing the analyte. We call this stoichiometric mixture the equivalence point. Unlike precipitation gravimetry , where the precipitant is added in excess, determining the exact volume of titrant needed to reach the equivalence point is essential. The product of the equivalence point volume, veq and the titrant’s concentration, Ct, gives the moles of titrant reacting with analyte.

Moles titrant=

Knowing the stoichiometry of the titration reaction (s), we can calculate the moles of analyte (Harvey, 2000 : 274).

Provided that the end point coincides with equivalence point or the stoichiometry of the reaction studied, theamounts of titrant and titrand measured should correspond to the actual amount present.

For a general reaction: aA + bB  cC + dD

A moles of a react with b moles of B to produce c moles of C and d moles of D. A molar solution contains 1 mole of solute per 1000 cm (or 1 L) of solution. Therefore, 1 cm of a 1 M solution contains 1 mmol of solute ( kealey, 2000: 81)

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The best indicator is one which gives the clear and sharp end point (easily discernable) at the exact equivalence point of reacting substance (angelova, 2007: 437).

The reactions employed in titrimatric analysis fall into four main classes. The first three of these involve no change in oxidation state as they are dependent upon the combination of ions. But the fourth class, oxidation-reduction reactions, involves a change of oxidation state or, expressed another way, a transfer of electrons.

1. Neutralization reactions, or acidimetry and alkalimetry. These include the of titration of free bases, or those formed from salts of weak acids by hydrolysis, with a standard acid (acidimetry), and the titration of free acids, or those formed by the hydrolysis of salts of weak bases, with a standard base (alkalimetry).

2. Complex formation reaction. These depend upon the combination of ions, other than hydrogen or hydroxide ions, to form a soluble, slightly dissociated ion or compound, as in the titration of a solution of a cyanide with silver nitrate () or of chloride ion with mercury (II) nitrate solution (). 3. Precipitation reactions. These depend upon the combination of ions to form a simple precipitate as in the titration of silver ion with a solution of a chloride

4. Oxidation-reduction reactions. Under this heading are included all reactions involving change of oxidation number or transfer of electrons among the reacting substance (vogel. 1989: 259).

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of HCl standard 0,1 N by added MD indicator, to determined bicarbonate in sample (Tim dosen, 2014:12).

The effective titrant concentration normally differs from the nominal concentration due to either inaccurate preparation, purity of titrant used, or changed due to instability. The effective concentration is determined by means of a titer determination or a titration of a substance of exactly known concentration usually a primary standard. It is essential to perform a titer determination on all titrants before used for the first time. This also applies to purchase reagents of certified concentration since the titer determination not only compensates for concentration errors but also any minor burette inaccuracies. This is a particular importance with corrosive bases since they attack the glasses walls 01 the burette resulting in small volume changes (John, 2001: 33).

Titration was carried out until color changes from colorless to pale pink. Results were obtained in triplicate for standardization using the following formula ---, (where N1 and V1 are the normality and N2 and V2 are unknown normality ( Asrelly, 2012: 765).

Although molar concentration are now commonly used in determinations of reacting quantities in titrimetric analysis, it has been traditional to employ other concepts involving what are known as “equivalent weights” and “normalities” for this purpose. In neutralization reactions the equivalent weight/normality concept is relatively straight forward, but for reduction- oxidation titrations it often requires an understanding of what are known as “oxidation numbers” of the substance involved in the redox reaction ( Vogel, 1989: 260).

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D. APPARATUS AND CHEMICALS 1. Apparatus

a. Beaker 500 ml 1 unit

b. Volumetric flask 250 ml 1 unit c. Analytical balance 1 unit d. Erlenmeyer flask 250 ml 6 units

e. Pipette 3 units

f. Volumetric pipette 2 units

g. Funnel 2 units

h. Washing bottle 1 unit

i. Spatula 1 unit

j. Watch glass 1 unit

k. Stative and clamp @ 2 units

l. Burette 2 units

m. Aluminium foil 1 piece

n. Filtering paper 3 pieces o. Tissue

2. Chemicals

a. Solution of concentrated chloride acid 0,1 N ( HCl) b. Indicator of methyl orange (MO)

c. Aquadest (H2O)

d. Borax (Na2B4O7.10H2O)

e. Solution of chloride barium (II) 10 % (BaCl2)

f. solution of mixture sample E. WORK PROCEDURE

1. Standardization of HCl Solution.

a. 0,4035 g of Na2B4O7.10H2O was weighed in analytical balance and it

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b. 25 ml of solution was taken by volumetric pipette into Erlenmeyer flask (used 3 Erlenmeyer flask).

c. 3 drops of MO indicator was added by pipette into each Erlenmeyer flask

d. Titration was done with standard solution until the color changed and titrant volume was written

e. The average of titrant volume was calculated and concentration of standard chloride acid (HCl) was determined

2. Determination of Carbonate and Bicarbonate Mixture.

a. 25 ml solution of mixture sample was placed in Erlenmeyer flask by funnel ( used 3 Erlenmeyer flask)

b. 3 drops of MO indicator was added by pipette into each Erlenmeyer flask

c. Titration was done with standard solution of chloride acid (HCl) 0,1 N until the color changed snd titrant volume was written (for 3 Erlenmeyer flasks)

d. The average of titrant volume was calculated as V1

e. 25 ml solution mixture sample was placed in Erlenmeyer flask by funnel (used 3 Erlenmeyer flasks) and drops of chloride barium (II) 10 % (BaCl2) was added by pipette into each Erlenmeyer falsk

f. The precipitate was let down and it was filtered by funnel and filtering paper \

g. The filtrate was collected in other Erlenmeyer flask

h. Indicator of MO was added by pipette into each Erlenmeyer flask i. Titration was done with standard solution until the changed of color

and titrant volume was written

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k. Amount of carbonate (CO3-) and amount of bicarbonate (HCO3-) were

determined

F. OBSERVATION RESULT

No Activity Result

1

2

Standardization of HCl solution : 0,4035 g Na2B4O7.10H2O was weighed 

diluted by water in volumetric flask until 100 ml  took this solution by used volumetric pipette 25 ml into Erlenmeyer  prepared 3 Erlenmeyer flasks (each flask contained 25 ml )  added 3 drops of MO (each Erlenmeyer flask)  did titration with HCl as standard solution.

a. Titration I

b. Titration II

c. Titration III

- Colorless solution  (added MO)  yellow solution (added HCl)  red solution.

- Volume of titrant = 6,0 ml - Colorless solution  (added

MO)  yellow solution (added HCl)  red solution.

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Mixture determination of carbonate and bicarbonate : 25 ml solution of mixture sample into 3 Erlemeyer  did titration with HCl as standard solution (added 3 drops of MO indicator previously).

a. Titration I

b. Titration II

c. Titration III

- Colorless solution  (added BaCl2 10 %)  turbid

solution (filtered) (added MO)  yellow solution (added HCl)  red solution.

BaCl2 10 %)  turbid

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G. ANALYSIS DATA

1. Standardization of HCl solution. - titrat volume (average) as V2 :

V2 = 6,00ml+5,50ml+6,00ml

3 V2 = 5,83 ml

Known :

V1 = 25,00 ml

W = 0,4035 g = 403,5 mg MW = 381,0 mg mole V2 = 5,83 ml

Asked : N HCl = …? Solution :

N HCl = V1 100,0 X2

eq mmoleX

W MW V2

N HCl =

25,00ml 100,0 X2

eq mmoleX

403,5mg 381,0mg/mmole 5,83ml

N HCl = 0,2500ml X2 eq

mmoleX1,059mmole 5,83ml

N HCl = 0,09082 N

2. Mixture determination of carbonate and bicarbonate - Titrant volume (average) as V1 :

V1 =

50,50ml+50,20ml+49,60ml 3

V1 = 50,10 ml

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V2 = 43,00ml+44,50₃ ml+45,00ml

V2 = 44,20 ml

Known :

V1 : 50,10 ml

V2 : 44,20 ml

N HCl : 0,09082 N

Asked :

a) Amount of CO3- b) amount of HCO3

-Solution :

a) CO3- = (V1−V2)X NHCl

2X25,00ml

CO3- = (50,10−44,20)ml X0,09082N

2X25,00ml

CO3- = 0,01072 N ~ 0,01072 mmole/ml

b) HCO3-= V2X NHCl

25,00ml

HCO3-= 44,20ml X_25,000,09082_ml N

HCO3-= 0,7168 N ~ 0,7168 mmole/ml

H. DISCUSSION

Titrimetry method known as volumetric method that was analysis quantitative that was basicly on stoichiometry of chemical reaction between analyte and titrant component. Titrant was added in analyte solution until reach certain amount until reach equivalent point. In titrimetry experiment was done 2 activity, that are:

1. Standardization of HCl solution.

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saving it was can happen from HCl properties that was hydroscopic, it means can adsorb water vapor that was there on its area, so the water that was bound will change its concentration and it was not constant in its saving. The aim to do standardization is for know the concentration of HCl as certain using of sodium tetraborax bicarbonate (Na2B4O7.10H2O), because it was primary

standard. sodium tetraborax bicarbonate solution was used because has constant concentration and constant in its saving also reacted as fast with HCl. Beside of that, sodium tetraborax bicarbonate that was weak base able to reacted with chloride acid. Its reaction :

Na2B4O7.10H2O (l) + 2HCl(l)  2NaCl(l) + 4 H3BO3(l) + 5H2O(aq)

After done the standardization then we done titration with observation of equivalent point also end point of titration, because all of that has relation. Sodium tetraborax bicarbonate was reacted with MO indicator in that problem indicator used for given mark when titration had been finished (determination of end point titration) also identification product from its mixture of solution. Titration is chemical analysis that was fast and accurate so it was certain to used for determination amount of component or substance in a solution. MO indicator given color in analyte and titration was done until 3 times with calculate volume average of titrant so we can knew the concentration of HCl solution standard. HCl solution was done as titrant. After done titration we gotten analyte color (sodium tetraborax bicarbonate) become red, that was mark that it was reach a equivalent point (amount of acid mole that was added same with the amount of base mole). MO indicator has section of pH = 3,1 – 4,4 that was acid properties from reaction that was done it is borax (H3BO3).

From titration that was done until 3 times so we got average volume of titrant is 5,83 ml so we gotten normality of HCl solution is 0.09082 N.

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Sample solution of carbonate and bicarbonate were reacted wit MO indicator that was resulted yellow color then done titration with chloride acid standard (HCl) so resulted red color. Titration about 3 times done for got the result (amount of carbonate) that more accurate. We gotten HCl volume about 50,5 ml, 50,2 ml, and 49,6 ml. so the average volume as 50,1 ml with carbonate amount as 0,01072 mmole/ml.

Determination of bicarbonate was done with reacted sample solution and several drops of barium (II) chloride 10 (BaCl2). After adding of BaCl2 10

% we gotten solution color become turbid also formed white precipitate. Adding of BaCl210 % has function for precipitate carbonate ion (CO3-) so in

sample solution just there in bicarbonate ion. Reaction between BaCl2 10 %

an carbonate ion will form BaCO3 precipitate then it was filtered for

separating precipitate and sample solution (bicarbonate). Sample solution then added with MO indicator for given mark mark (color change) when end titration (determination of end point titration) also identification product from mixture solution, then gotten the color of sample solution become yellow. Titration done 3 times with using chloride acid solution (HCl) resulted color o0f solution become red. Finally the volume of titrant that was gotten are 43,1 ml, 44,5 ml, and 45,0 ml so the average volume of titrant is 44,2 ml with carbonate amount 0,1768 mmole/ml. the reaction is :

BaCl2 (l) + CO3-(l)  BaCO3 (s) ↓ + 2 Cl-(l)

HCO2(l) + HCl (l)  H2CO3(l) + Cl-(l)

I. CONCLUSION

According to experiment, we may conclude that :

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2. Determination of carbonate and bicarbonate have been getting each amount are 0,01072 mmole/ml and 0,1768 mmole/ml, respectively

J. SUGGESTION

1. Apperentice should pay attention with significant number in every apparatus needed so that calculation can be correct.

2. Apperentice and assistant should carefull in doing teamwork to get accurate result.

BIBLIOGRAPHY

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Pharmacy. (online). Vol. 2 no. 4 page 765. (accessed on November 10th_,

2014).

Angelova, R., et.al. (2007). Comparative Study of Titrimetric Methods For Determination of Organic Carbon In Soils, Compost, And Sludge. Journal of International Scientific Publications : Ecology anf Savety. (online). Vol. 8. Page 437 (accessed on November 10th_{, 2014)}

Harvey, David. 2000. Modern Analytical Chemistry. USA : DePauw University

John. 2001. Basic of Titration. USA : Cambridge University

Kealey, D., et. al. 2005. Instant Note Analytical Chemistry. UK : University of Leeds Tim Dosen. 2014. Penuntun Praktikum Kimia AnalitikI. Makassar :UNM

Vogel., et. al. 1989. Testbook of Quantitative Chemical Analysis. UK : Longman Group

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The complete report of Analytical Chemistry I with the tittle “Titrimetry” that was made by :

Group : II (two)

Class : ICP B Chemistry

This has been checked and consulted by assistant and assistant coordinator, so this report is accepted.

Makassar, January 2015

Assistant coordinator, Assistant,

(Lukmanul Hakim S) (Lukmanul Hakim S)

Known by responsibility Lecturer,