Neutralization Titration.pdf - NEUTRALIZATION TITRATIONS...

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1 NEUTRALIZATION TITRATIONS AIM The main objective of this experiment is to determine weak acids in an unknown solution by using titrimetry. INTRODUCTION Neutralization of hydronium or hydroxide ion to form water is widely used as the basis for volumetric determinations of acids, bases and salts of weak acids. The reaction is characterized by a rapid change in pH near the equivalence point, a change that is readily detected by an acid-base indicator or that can be followed electrically by use of a pH meter. Neutralization titrations are performed with standard solutions of strong acids or strong bases. A standard solution (or standard titrant) is a reagent of exactly known concentration. Standard solutions play a central role in all volumetric methods of analysis. The ideal standard solution for a volumetric method should - be sufficiently stable so that it will not be necessary to determine its concentration (to standardize it) so frequently. - react rapidly with the analyte so that the time required between each addition of the titrant is minimized. - react more or less completely with the analyte so that satisfactory end points are realized. - undergo a selective reaction with the analyte that can be described by a simple balanced equation. The accuracy of a volumetric method is closely related with the accuracy of the concentration of the standard solution used in the titration. Two basic methods are used to determine the concentration of standard solutions: In the direct method, a carefully weighed quantity of a primary standard is dissolved and diluted to an exactly known volume in a volumetric flask. In the second method, the solution is standardized by titrating: - a weighed quantity of a primary standard - a weighed quantity of a secondary standard or - a measured volume of another standard solution. As a result, standardization is a process of determining the concentration of a substance in solution by adding a standard reagent of known concentration to it in carefully measured amounts until a reaction of definite and known proportion is completed and then calculating the unknown concentration. A titrant that is standardized against a primary standard or against a standard solution which is called as a secondary solution. A secondary standard is less desirable than a primary standard solution, because the concentration of the former is subject to greater uncertainty. A primary standard is a highly purified compound that serves as a reference material in all titrimetric methods. Important requirements for a primary standard are: - High purity - Stability in air
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