0929Update

0929Update - pKa Methyl Red Introduction: The relationship...

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pKa Methyl Red Introduction: The relationship between light absorption and concentration can be investigated according to the Beer-Lambert Law: A= EL[x] (fix later). An experimental determination of E can be performed using the acid and base components of a weak acid such as methyl red. Due to overlap in the absorption ranges, two equations are set up with two unknowns so that E can be solved based on the aborbances of the two buffers at two different wavelengths. The wavelengths are selected at the max aborbance of each of the two buffers. Theory: Procedure: A .05% stock solution of methyl red was pre-made. This solution was created by dissolving 0.028g of methyl red in 20mL 95% ethanol in a 50 mL volumetric flask. Then, this was diluted almost to the mark, leaving room for the drop-wise addition of .1M NaOH to get all of the solid to dissolve. The volume was then brought to 50 mL, and 20 mL of this solution was put into a 200 mL volumetric flask, and 50mL 95% ethanol was added. Finally, this solution was diluted to the mark using water. A basic solution of methyl red was prepared by adding 10mL of 0.100 M sodium acetate in a 100 mL volumetric flask, and 10 mL from the methyl red stock solution and 9ml of 1.0 M potassium chloride were added. An acidic solution of methyl red was prepared by adding 10 mL of 0.100 M acetic acid, and 10ml from the methyl red stock solution and 10ml of 1.0 M potassium chloride was added. Two burets were filled, one with the acidic
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0929Update - pKa Methyl Red Introduction: The relationship...

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