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TBC 3013TBC 3013

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LECTURER : DR ROSMILA MISNAN LECTURER : DR ROSMILA MISNAN

Acid-base titration report Acid-base titration report

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NAME MATRIC NO.

UMI ABIBAH BT SULAIMAN D20091034811

SITI RAHAYU BT MOHAMED NOOR D20091034855

NUR AFIQAH BINTI MUHAMAD

APANDI

D20091034872

AMEERA BT YAHYAD20091034814

ABSTRACABSTRACTT

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 NaOH 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.

INTRODUCTIONINTRODUCTION laboratory method of quantitative

analysis used to determine unknown concentration of known substance.

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.

Titration

Pka value

METHOD:

ACID BASE TITRATION

METHOD : ACID BASE TITRATION

Calibrated pH meterTitration apparatus

Titration in progress

Table : Volume of NaOH used and the pH values recorded

RESULTRESULT

Graf 1: Graf 1: pH pH vs Volume of NaoH vs Volume of NaoH (Acetic Acid) (Acetic Acid)

pKa1=5.52

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.

Graf 2: Graf 2: pH pH vs Volume of NaoH vs Volume of NaoH (Phosphoric Acid) (Phosphoric Acid)

pKa1=3.21

 pKa2=7.44

pKa3=12.24

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.

The pKa from the experiment result was not too accurate compare to the theoretical value. This might be happened because of:

pH meter used also not too

suitable and not measured the accurate pH

reading.

Not precisely added 1ml of

0.1M NaOH for every step

titration process.

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.

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.

CONCLUSIONCONCLUSION

As a conclusion,

able to identidy the pKa of an acid by using titration.

learn how to use pH meter correctly.

REFERENCEShttps://docs.google.com/viewer?

a=v&q=cache:hWqGYixWkLsJ:www2.chem.ubc.ca/courseware/330/pKa.pdf+&hl=en&gl=my&pid=bl&srcid=ADGEESi0c85vsFbBU4uwyfTNi2oMOBB8prpi05jtfiPOheSrjLORUpXTvhvoLAAALjoQweS1utzrEGWeJkbUGBuwsixCBSHf3ULXuzjHyDGhG4MAQNjL86hdoGlCTWzD0Hc6v12ZMAI0&sig=AHIEtbTBuPkVBPk4IcMmhHj7n0u1hNGnXw

https://docs.google.com/viewer?a=v&q=cache:oOMX3c6_bfoJ:www.deltacollege.edu/emp/ckim/Labs_PDF/AcidBaseTitrationCurveLab.pdf+&hl=en&gl=my&pid=bl&srcid=ADGEESjl3hlEXLOO2UI_DXZGy35s8xAPURLrBVvoCgc7WH8O1lWP4yTZuSvdNhoEgwdMKoVoXJsSIFhktON_PWOttJPKukddWLfQGe7UChJESb0bPka_sPmk81gIvaAQE8o7lrIa1CAl&sig=AHIEtbRprjL5NExSdDjM_UtF5F-LJ4hdvQ

THANK YOU!!!!