Determination of Ionization Constant of a Weak Acid by Potentiometric Titration

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Determination of Ionization Constant of a Weak Acid byPotentiometric TitrationMendoza, Ronel A.School of Chemistry and Chemical EngineeringMAPUA Institute of TechnologyAbstractThis experiment aims to scrutinize the underlying principles in the determination of ionizationconstant of a weak acid by potentiometric titration. Potentiometric titration involves determination of thepotential of a suitable indicator electrode as a function of titrant volume. In the previous experiment, acid-base titration was performed to determine the concentration of a specific solution. However, there weremoments when an appropriate indicator does not exist. This means that the color of the solution isobscuring the color change that associates the equivalence point of the solution. A normal mechanicalassembly to perform a manual potentiometric titration includes measuring and recording the cell potential(in units of millivolts or pH) after every addition of a reagent. This analysis was done by the usage ofdigital pH meter for pH measurement as the base titrant is added at different volume intervals. At the endof the experiment, we were not able to get the pKa of our unknown sample.Keywords:Potentiometric titration, ionization constant, pH, pKa, weak acidINTRODUCTIONThe objective of the experiment wasfor laboratory student to know theunderlying principles of potentiometrictitration. Proper techniques in potentiometrictitration were done to have a good result.Lastly, this experiment aims to determinethe ionization constant of a weak acid. Themain objective was to determine the identityof your unknown from the calculatedequivalent weight and estimated pKa.In a potentiometric titration onemakes a diagram of the volume of titrantconveyed from a buret against the voltage(or some capacity straightforwardlyidentified with the voltage, for example, pH)delivered by two electrodes in the solutionbeing titrated. Provided the equilibrium of
the analytical reaction is favourable what'smore, one picks the right blend of electrodesthere will be a sharp change in voltage at theequivalence point. This adjustment involtage can be utilized as a part of spot of acolor indicator to find the equivalence point.This is clearly an extremely valuable systemif one is managing a shaded arrangement inwhich an indicator would be futile or in aframework for which a suitable indicatordoes not exist. Data obtained bypotentiometric titrations are more reliablethan data gathered from titrations thatinvolves the usage of chemical indicatorsand are specifically very important withcolored or turbid solutions and for thedetection of the presence of unsuspectedspecies.

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Term
Spring
Professor
Dr. Dahlia C. Apodaca
Tags
pH, Equivalence point

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