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Unformatted text preview: Introduction: In our complexometric titration experiment, there were many objectives that we made sure to complete in order to arrive at our final data. The first of our many objectives was to prepare a proper NaOH solution given the number of moles, as well as match it up with the correct amount of Potassium Hydrogen Phthalate. These measurements were crucial in order to maintain a proper titration curve, and anything off would have thrown the whole experiment off. The next objective was to perform the same titration experiment, but instead of a known sample, we were given 3 different compounds, each which was unknown to the testers. We were go about our titration methods to finally come about a final molecular weight as well as pka value for the unknown weak acids. It is pertinent to know some background information before beginning the weak acid titration experiment. It is necessary to understand how a pka and ka value are calculated, as well as what the graph of these weak acid titrations should look like. By knowing this background before beginning your tests, you can take note of how the curve should look and what values you are looking for in particular. Discussion: In this two week experiment, the main purpose was to try and distinguish what the unknown weak acids given to us were, as well as test our NaOH solution to make sure the concentration was adequate enough to complete the experiment. Looking at the data is not enough to realize which weak acid we were presented with, but rather many calculations were also needed. In the instance of sample weak acid A1, one was to look at the pH vs. mL of NaOH added graph to distinguish an equivalence point from which you can find a half equivalence. These two points are crucial in finding the unknown solutions pka values, which are significant identifying weak acids from each other. So in the first graph of A1, the equivalence point can be found close to the top of the graph (around 18 mL), which leads us to look at our half equivalence point at 9 mL. The corresponding pH at this mL value gives us the pka for A1, which turns out to be 3.69. This value is taken into consideration when looking at the given weak acid chart, as comparing the molar mass of A1 ( as seen in the calculation section) which turns out to be 95.7 g/mol and the pka value, one can arise at a conclusion that A1 is Lactic Acid ( which had a pka value of 3.86 and a molar mass of 90.08). The next unknown weak acid that we tested was C1, which after calculations and observations, was determined to be Acetic Acid. The values corresponding to this unknown acid were a molar mass of 62.16 g/mol with a pka value of 3.95. Finally the third unknown weak acid that was tested was C3, which was determined to be Glycine, had a molar mass of 61.11 g/mol with a pka value of 2.42. By comparing our measured values to the weak acid chart, the conclusion was drawn that this could possibly be our...
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 Spring '08
 Grall
 Chemistry, Mole

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