weak acid titration lab report

weak acid titration lab report - Introduction: An essential...

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Introduction: An essential characteristic of a weak acid is that it disassociates into ions only very little and that most of their molecules remain intact. Examples of weak acids include hydrofluoric acid (HF) and acetic acid CH 3 COOH. A crucial example of equilibrium chemistry involves a reaction that has water and weak acids. In aqueous solutions, weak acids react with water in the following manner: HA+H 2 0 - H 3 0+A - The weak acid dissocation constant, also known as K a , is written in the following manner and is meant to represent the relative concentrations of the components of this equilibrium: K a = [H 3 0+]eq [A-]eq [HA]eq The [ ] denotes the equilibrium concentration in terms of moles/L. The weak acid dissociation constant is constant at a given temperature for a given acid. In order to find the K a for a weak acid, this requires establishing a proper equilibrium and then measuring the concentrations of all three components. In order to attain the hydronium ion concentration, a pH electrode is used. In order to obtain the other concentrations, spectroscopy can be used. In investigating the titration of a weak acid and a strong base, a graph can be used that has volume of strong base on the x-axis and pH on the y-axis. The buffer region on this curve is defined as the region where 10% of the weak acid has been titrated but less than 90% has. The buffer region is used to help determine the value of Ka. If one wants to know the identity of an unknown weak acid, then two characteristics that one should look at are the molecular mass of the unknown acid and the pKa value of this acid. The pKa value can be attained by the following equation: 1
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pH= pK a + log ( Vb/Vb equiv -V b ) This equation can be used to find the pK a value. There are many experimental objectives behind performing a weak acid titration. These objectives include making simultaneous volume and pH measurements, preparing and standardizing a strong base solution, determining the molecular weight of the weak acid from titration data, and determining the identity of an unknown weak acid. My expectations for this lab are that if the human error can be limited to a
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This essay was uploaded on 04/11/2008 for the course MUS 334 taught by Professor Shaheen during the Spring '08 term at Arizona.

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weak acid titration lab report - Introduction: An essential...

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