ACID BASE TITRATION
Introduction
Acid base
titration is an experiment where a known concentration of acid or base is used
to infer an unknown concentration of base or acid. Titrations are often used to
determine the pH of certain solution.
A titration
curve can be plot from the titrant volume and pH obtained from titration. The
titration curves lies much interesting chemistry about the acids and bases. The
inflection point of the titration curve is the equivalent point. It is a point
where the reaction is neutralized. From the titration curve, we also can see
buffering region before the equivalent point. In the buffering region, it takes
large amount of NaOH to produce a small change in pH of the receiving solution.
Materials
0.1M acetic acid, 0.1M phosphoric acid, 0.1M NaOH, pipette, burette, retort stand, calibrated pH meter
Method
Result
a) Acetic acid
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| Graft Acetic acid |
b) Phosphoric acid
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| Graft Phosphoric acid |
Discussion
Acid is
chemical that release a proton (H+) and have pH below 7. While, base is
chemical that accepts proton (H+) and have pH above 7. Acid are classified as
either strong or weak based on their ionization in water. A strong acid is an
acid which completely ionized in an aqueous solution, while a weak acid is an
acid which ionized slightly in an aqueous solution. In this experiment, we
tested an acetic acid and phosphoric acid with NaOH (strong base) to observe the
property of weak acid with pH changes. The value of pKa was determined based on
the graph of pH versus volume of NaOH (strong base) using geometric method.
Beside that, the point of inflection at the graph was chooses as an indicator
to tell when the acid and base mixed in exactly the righr proportions to
‘neutralize’ each other. We also can know the midpoint and pKa for the acid
from the equivalence point. Each acid have their own shape of graph due to
their reaction with the base.
In this experiment, we can determine types of acid based on the shape of their graphs. The graph of acetic acid of pH versus volume of NaOH(base) show that acetic acid is monoprotic which have only one hydrogen that can be neutralized. Beside that, its only have one pKa which is 4.4. While, the graph of phosphoric acid of pH versus volume of NaOH(base) shows that phosphoric acid is polyprotic which have more than one hydrogen that can be neutralized. However, we can not determined the pKa value for phosphoric acid due to errors.
From this experiment,
I have learnt to find the pKa of acid from the titration curve. The half value
of equivalent point is determined. The pH value at the half-eqivalent is equal
to the pka. Buffer system also can be prepared through acid-base titration. The
buffer prepared is most effective when it is nearest to pKa.
In this experiment, we can determine types of acid based on the shape of their graphs. The graph of acetic acid of pH versus volume of NaOH(base) show that acetic acid is monoprotic which have only one hydrogen that can be neutralized. Beside that, its only have one pKa which is 4.4. While, the graph of phosphoric acid of pH versus volume of NaOH(base) shows that phosphoric acid is polyprotic which have more than one hydrogen that can be neutralized. However, we can not determined the pKa value for phosphoric acid due to errors.
Conclusion
As a conclusion, from this experiment we observed the property of weak acid with pH changes. The pKa of acetic acid is 4.4 and not much different from theorytical value.
Reference
As a conclusion, from this experiment we observed the property of weak acid with pH changes. The pKa of acetic acid is 4.4 and not much different from theorytical value.
Reference
Katz, S.,
& Beatson, R. P. (1984). The determination of strong and weak acidic groups
in sulfite pulps. Svensk papperstidning, 87(6), 48-53.
Goddu, R.
F., & Hume, D. N. (1954). Photometric titration of weak acids. Analytical
Chemistry, 26(11), 1679-1684.
Reflection
A) CHRIS
ROXA ANGELLA SUPAIN (D20141067094)
From this experiment that we had
conducted which is acid-base titration, I had learnt the property of weak acid
with pH change. Besides that, I had learnt how to use new apparatus for me which
is pH meter because usually we use litmus paper to determine the pH value. The
pH meter must be use gently since it have highly sensitive sensor. Other that,
from this experiment my titration skills was improved. On previous experiment,
I usually over titrated the solution however in this experiment I learnt how to
minimize the error during titration. One of the skill I improved is when
reading a burette it is important that our line of sight be in a direction
perpendicular to the burette column. Last but not least, I learnt the
importance of teamwork among the group. We are helping each other to set up,
conduct and clean up the experiment. Overall, I gain a lots of skills and
experience by this experiment.
B) TING
MEE PING (D20141067055)
C)LENDRA NALAT ( D20141067021)
In this experiment, I have learned that cooperation and teamwork between your group members is very important to do all task. Beside that, I also learned to be responsible to do works that have been given to me. I also learned to always be precautions and be carefull especially when handling a chemical that can cause harm to us.
In this experiment, I have learned that cooperation and teamwork between your group members is very important to do all task. Beside that, I also learned to be responsible to do works that have been given to me. I also learned to always be precautions and be carefull especially when handling a chemical that can cause harm to us.
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| pH meter |
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| burette and retort stand |
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| Titration process |
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