AcidBase Titration
Posted 2 Juli 2008
on:ACIDBASE TITRATION
I. Objective
Students can acquire knowledge and ability in determining concentration of the solution by divalen acidbase titration (H_{2}SO_{4}) by using phenoltalein indicator (PP).
II. Theory
According to Bronsted and Lowry, an acid is a species which donates a proton, H^{+}, and a base is a species which accepts a proton in a protontransfer reaction.
For example, in the following acidbase reaction:
H_{2}SO_{4} _{(aq)} + 2NaOH _{(aq)} → 2H_{2}O _{(l)} + 2Na^{+ }_{(aq)} + SO_{4}^{2–}_{ (aq)}
H_{2}SO_{4} _{(aq)} is an acid which donates a proton, H^{+}, to the base NaOH _{(aq)}. This reaction is often called a neutralization reaction.
An acidbase titration is a procedure for determining the concentration of an acid (or a base) in a solution by measuring the volume of base (or acid) of a known concentration that completely reacts with it.
The solution of accurately known concentration is called the standard solution (titrant), it contains a definite number of gramequivalents per liter. Standard solution is usually added from a graduated vessel called a burette. The process of adding titrant until the reaction just complete is termed a titration and the substance to be determined is titrated (analyte). The point at which the reaction is complete is called the equivalence point or the theoretical (or stoichiometric) end point. This point must be detectable by some change unmistakable to the eye and this can be done by adding an auxiliary reagent, known as an indicator which should give a clear visual change (color change) in the liquid being titrated.
In order to perform a titration procedure a reaction must fulfill the following condition.
1. It must be simple reaction, which can be expressed by a chemical reaction. The substance to be determined should react completely with the titrant in stoichiometric or equivalent proportions.
2. The reaction should be practically instantaneous or proceed with very great speed.
3. There must be a marked change in some physical or chemical property (as color change) of the solution at the equivalence point.
4. An indicator should be available which, by a change in physical properties (Color), should sharply define the end point of the reaction.
5. If no visible indicator is available for the detection of the equivalence point, the latter can often be determined by other method as potentiometer or conduct metric or spectrophotometer titration.
Titration can be used for many types of reactions:
a. Neutralization (reaction of acid with base.).
b. Precipitation reaction.
c. Oxidation – reduction reactions
d. Complex formation reactions.
III. Materials and equipments
v Materials
NaOH solution 0,1 N
H_{2}SO_{4}_{ }solution x N
Phenolphthalein Indicator (PP)
v Equipments
Burette 50 mL 1 pcs
Erlenmeyer flask 250 mL 2 pcs
Drooping Pipette 2 pcs
Graduated Glass Cylinder 50 mL 2 pcs
Stirring Stick 1 pcs
Funnel 1 pcs
Volumetric Pipette 10 mL 1 pcs
Stand, retort and klem (stative) 1 set
IV. Procedure
 Equipments are set for titration process
 Burette is washed up with aquades and the tap’s leakage is checked accuracy.
 Burette is washed up with some titrant (NaOH 0,1 N).
 Titrant (NaOH 0,1 N) are entered into burette using funnel to zero numeral.
 10 mL titrated (H_{2}SO_{4}) are entered into Erlenmeyer flask.
 Titrated are added phenoltalein indicator (PP) around 12 crop.
 Titration is done by drooping titrant into titrated bit by bit from burette.
 Titration are stopped until the titrated’s color changed.
 Titrant volumes are written down.
 59 procedure are repeated 3 times.
 Average titrant’s volume that used are calculated.
 Unknown concentration of solution are calculated.
V. Observe result
Observe table of H_{2}SO_{4}_{ }solution.
Repeating 
Volume 

Titrate Volume (H_{2}SO_{4}) 
Titrant Volume (NaOH 0,1 N) 

1 
10 mL 
9,6 mL 
2 
10 mL 
9,1 mL 
3 
10 mL 
9,4 mL 
Average Volume 
10 mL 
9,4 mL 
VI. Discussion
The experiment that we did is name alkalimetri titration because it is done to determine concentration of acid solution (H_{2}SO_{4}) by using base standard solution (NaOH 0,1 M). The titrated in this experiment is H_{2}SO_{4} x M around 10 mL. PP indicator is added to differentiate acid solution with base solution so that by adding 2 drops PP indicator in H_{2}SO_{4} x M make the H_{2}SO_{4} x M solution still uncolored. Then in the titrated is titrationed by NaOH 0,1 M solution. This procedure is repeated 3 times. End point indication of titration is the changed of titrated color from uncolored into red when the volume of NaOH 0,1 M solution is used around 9,6 mL;9,1 mL; and 9,4 mL each other.
Next, will be done a calculation of concentration based on the theory and the experiment’s result.
For H_{2}SO_{4}_{ }Tirtation with NaOH as titrant :
Reaction between H_{2}SO_{4}_{ }and NaOH is:
Reaction: H_{2}SO_{4 (aq)} + 2NaOH_{(aq) }Na_{2}SO_{4 (aq) } + 2H_{2}O_{(l)}
From reaction above we can know that the ratio of mol between H_{2}SO_{4} and NaOH is 1:2. So, to calculate concentration of H_{2}SO_{4} solution based on the experiment’s result, we can use the equation below:
mmol ion H^{+} = mmol ion OH^{–} Ma . x . Va = Mb . n . Vb 
Information: Ma = acid molarity H_{X}A
Mb = strong base molarity L(OH)_{n}
_{ } Va = acid volume
Vb = base volume
X = acid valence
n = base valence
According to The Theory :
To determine NaOH solution’s volume that needed:
Titrant (NaOH) that used: 0,1 N same as 0,1 M (because it is monovalen).
Titrated (H_{2}SO_{4}_{)} that used: 0,1 N same as 0,05 M (because it is divalen). This concentration is acquired based on the calculation H_{2}SO_{4}_{ }concentration that made by group 2 and laboratory assistant.
Ma . x . va = Mb . n . vb
0.05 M . 2 .10 mL = 0,1 M . 1 . vb
1 mL = 0,1 . vb
Vb = 1 mL / 0,1
= 10 mL
So, to calculate H_{2}SO_{4 }0,05 M need 10 mL NaOH 0,1 N (based on the theory)
Based on the experiment’s result :
Experiment I (needed NaOH around 0,96 mL)
Ma . x . va = Mb . n . vb
Ma . 2 . 10 ml = 0,1 M . 1 . 9,6 ml
Ma . 20 ml = 0,96 mmol
Ma = 0,96 mmol/20 ml
= 0,048 M
Experiment II (needed NaOH around 0,91 mL)
Ma . x . va = Mb . n . vb
Ma . 2 . 10 ml = 0,1 M . 1 . 9,1 ml
Ma . 20 ml = 0,91 mmol
Ma = 0,91 mmol/20 ml
= 0,0455 M
Experiment III (needed NaOH around 0,94 mL)
Ma . x . va = Mb . n . vb
Ma . 2 . 10 ml = 0,1 M . 1 . 9,4 ml
Ma . 20 ml = 0,94 mmol
Ma = 0,94 mmol/20 ml
= 0,047 M
Calculate using average volume:
Ma . x . va = Mb . n . vb
Ma . 2 . 10 ml = 0,1 M . 1 . 9,4 ml
Ma . 20 ml = 0,94 mmol
Ma = 0,94 mmol/20 ml
= 0,047 M
Calculate using average molarity:
Average morality of H_{2}SO_{4} = (0,048 M + 0,0455 M + 0,047 M)/3
= 0,0468 M = 0,047 M
So from the whole of experiment we get concentration of H_{2}SO_{4} solution is 0,047 M
The difference of molarity:
The difference = M – M experiment
= 0,05 M – 0,047 M
= 0,003 M
Based on the calculation from the experiment’s result and the real concentration of H_{2}SO_{4}_{, }we can know that the relative mistake from the titration is:
The relative mistake : (0,05 M – 0,047 M) x 100 % = 6 %
0,05 M
From the difference above, there are view mistakes of concentration between concentration H_{2}SO_{4} that used and concentration that acquired from the result of calculation NaOH volume that used. It is caused by:
1. Accurate less of titration process.
2. There is a leakage on titration tool.
3. The titration tool is not working well, we can see from the accurateness number.
4. Accurate less of solution’s making process.
5. Accurate less in noting the color change of indicator.
VII. Conclusion
1. Titration is used to determine solution’s concentration with reacting some solution’s volume into some other solution which its concentration has known before.
2. The end titration’s point is marked by the color changed of the titrated.
3. Adding PP indicator is used to differentiate whether it is acid or base solution.
4. Thus, from the titration’s result, we acquire H_{2}SO_{4}_{ }concentration is 0,047 M, on the other hand from the liquiding’s result we acquire H_{2}SO_{4}_{ }concentration is 0,05 M. It happens may be because of accurate less of liquiding H_{2}SO_{4}. Beside that it is also caused by accurate less in titration process..
VIII. Booklist
1. Sunardi.2007. Buku Kimia untuk SMA/MA kelas XI. Yrama Widya : Bandung
2. Brady, JE.1999. Kimia Universitas Azas dan Struktur. Jilid 1 edisi ke5, alih bahasa Sukmariah Maun, Kamanti Anas, Tilda S. Sally. Jakarta : Binarupa Aksara
3. Simamora, Maruli, dkk. 2004. Buku Ajar Kimia Dasar 2. Singaraja : IKIP Negeri Singaraja.
4. Subagia, I Wayan dan Suhemi Sya’ban. 2005. Materi Praktikum Kimia Dasar 2. Singaraja : IKIP Negeri Singaraja.
5. Syukri. 1999. Kimia Dasar II. Bandung : ITB
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