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Determination of Ionization Constant of a Weak Acid by Potentiometric TitrationMendoza, Ronel A.School of Chemistry and Chemical EngineeringMAPUA Institute of TechnologyAbstractThis experiment aims to scrutinize the underlying principles in the determination of ionization constant of a weak acid by potentiometric titration. Potentiometric titration involves determination of the potential 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 were moments when an appropriate indicator does not exist. This means that the color of the solution is obscuring the color change that associates the equivalence point of the solution. A normal mechanical assembly 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 of digital pH meter for pH measurement as the base titrant is added at different volume intervals. At the end of 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 was for laboratory student to know the underlying principles of potentiometric titration. Proper techniques in potentiometrictitration were done to have a good result. Lastly, this experiment aims to determine the ionization constant of a weak acid. The main objective was to determine the identityof your unknown from the calculated equivalent weight and estimated pKa.In a potentiometric titration one makes a diagram of the volume of titrant conveyed from a buret against the voltage (or some capacity straightforwardly identified with the voltage, for example, pH)delivered by two electrodes in the solution being titrated. Provided the equilibrium of the analytical reaction is favourable what's
more, one picks the right blend of electrodesthere will be a sharp change in voltage at theequivalence point. This adjustment in voltage can be utilized as a part of spot of a color indicator to find the equivalence point.This is clearly an extremely valuable systemif one is managing a shaded arrangement in which an indicator would be futile or in a framework for which a suitable indicator does not exist. Data obtained by potentiometric titrations are more reliable than data gathered from titrations that involves the usage of chemical indicators and are specifically very important with colored or turbid solutions and for the detection of the presence of unsuspected species.