1. ACid-BAse TiTrATion reporT
USER NAME : TBC 3013
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PASSWORD :
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LECTURER : DR ROSMILA MISNAN
2. GROUP MEMBERS
NAME MATRIC NO.
UMI ABIBAH BT SULAIMAN D20091034811
SITI RAHAYU BT MOHAMED NOOR D20091034855
D20091034872
NUR AFIQAH BINTI MUHAMAD APANDI
D20091034814
AMEERA BT YAHYA
3. ABSTRACT
The main objective of this study was to investigate the
property of weak acid with pH changes.
Result was collected from the pH meter during the
titration of acetic acid and phosphoric acid with 1mL of
0.1M NaOH .
The graph pH against volume of acid is plotted and the pKa
value was determined. Both acid have different pKa value
and horizontal part of the curve.
The study recommends that the larger the value of pKa, the
smaller the extent of dissociation while the smaller the pKa
value the higher the extent of dissociation.
4. INTRODUCTION
Titration laboratory method of quantitative
analysis used to determine unknown
concentration of known
substance.
Pka value can determined pKa of an
acid from the graph.
value used to describe the
tendency of compounds or ions
to dissociate.
This allows the proportion of neutral and charged species
at any pH to be calculated, as well as the basic or acidic
properties of the compound to be defined.
10. Graf 1: pH vs Volume of NaoH
(Acetic Acid)
pKa1=5.52
11. To calculate the acid dissociation constant (pKa), one must
find the volume at the half-equivalence point, that is where
half the amount of titrant has been added to form the next
compound.
From the graph plotted the pKa for acetic acid is 5.52
compare to the theoretical value which is 4.76.
Halfway between each equivalence point, at 4 mL ,the pH
observed was about 5.52 , giving the pKa.
12. Graf 2: pH vs Volume of NaoH
(Phosphoric Acid)
pKa3=12.24
pKa2=7.44
pKa1=3.21
13. Then, the pKa value for phosphorus acid
accoding to the graph are 3.21,7.44 and
12.24 compare to the theoretical value
which are 2.15,7.20 and 12.35.
Halfway between each equivalence point,
at 4 mL , 12.5 mL and 19.5, the pH
observed was about 3.21, 7.44 and
12.24 , giving the pKa.
14. The pKa from the experiment result was not
too accurate compare to the theoretical value.
This might be happened because of:
Not precisely added pH meter used also
1ml of 0.1M NaOH not too suitable and
for every step not measured the
titration process. accurate pH reading.
15. The pKa of an acid can be determined from the
part of the graph having flat or more horizontal
part of the curve.
The larger the value of pKa, the smaller the extent
of dissociation while the smaller the pKa value
the higher the extent of dissociation.
Inflectionpoint is important to determine the
point of neutralization of acid by titrant.
16. For acetic acid one horizontal part on the
curve
For phosphoric acid three horizontal parts
The difference arise
Due to acids having one or more than one
dissociation constant in order for all the H+ ions
can react completely with the OH- ions being
added during the titration process.
17. CONCLUSION
As a conclusion,
able to identidy the pKa of an acid by
using titration.
learn how to use pH meter correctly.
