# Determination of the Dissociation Constant of a Weak Acid.docx

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C a n d e l a r i a | 1Determination of theDissociation Constant of aWeak AcidDaniel Candelaria Jr.Partner: Michelle GrecniCHE 121-03Dr. Yigui WangApril 9, 2013
C a n d e l a r i a | 2Purpose:To become familiar with using a pH meter and determining the equivalence point of an acid-basesolution as well as finding the one half equivalence point using the technique of titration, and determining the amount of acid in an unknown. Introduction:Johannes Brønsted, a chemist, and Thomas Lowry, a scientist, realized that the important event in most acid-base reactions is simply the transfer of a proton from one particle to another. Acids are substances that donate protons and bases are substances that accept protons. The term used for reaction of an acid with a base is neutralization. In this experiment, the neutralization of NaOH with an unknown acid will be used to determine the equivalence point by using a pH meter. Many solutes affect the pH of an aqueous solution. A pH meter consists of a meter and two electrodes. The measurement of pH requires two electrodes, one electrode senses H3O+, being sensitive to its concentrations and a reference electrode. In order to find the equivalence point, a titration will be performed which is an analytical procedure in which a solution of an unknown concentration is combined slowly and carefully with a standard solution until a signal shows that the equivalent quantities have reacted. By titrating a weak acid with a strong acid, the determination f the ionization constant can be determined. In order to do this, the recording of the pH versus the volume of the base added will be needed. From the titration curve received from plotting the recordings, the point revealing half the equivalence point would equal:[HA] = [A-]The standard deviation of Kawill be determined as well as the standard deviation of the amount of unknown acid using the formula:

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