Materials And Methods Of The Acid Solution

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MATERIALS AND METHODS: Before the acetic acid solution could be titrated with sodium hydroxide (NaOH), the actual concentration of NaOH needed to be determined. By way of standardization, the actual concentration of NaOH was established, to account for the fact that the solid is not pure and for its tendency to react with carbon dioxide in the air. A 50 mL burette (±0.01 mL, Kimax) was rinsed thoroughly, twice with reverse osmosis water, and then twice with approximately 5 mL of ~0.25 M NaOH solution (Fisher Scientific, Certified ACS Pellets, S318-3). A 125 mL Erlenmeyer flask (Fischer) was obtained and 0.999 g of potassium hydrogen phthalate (KHP, C8H5KO4) (Acros Organics, 99+%, Code: 417955000, Lot: A0358893) was added. A precision balance (±0.001 g) was used to ensure the weight was recorded to three decimal places. To dissolve the KHP, 25 mL of reverse osmosis water, measured with a 10 mL pipet (±0.01 mL), was pipetted into the flask and mixed thoroughly to form a solution. Three drops of the indicator, phenolphthalein, was added to the flask containing the dissolved KHP. The burette was then filled with ~0.25 M NaOH, using a glass funnel, and a small amount was drained in order to remove the remaining air from the tip. The initial volume of the burette was recorded to the nearest hundredth milliliter. The flask was placed under the burette and slowly, the NaOH was drained into the KHP solution, with constant mixing. The burette continued to be drained until the KHP solution changed from a clear color, to a persistent light pink, indicating the end point of the standardization. The final volume of the burette was recorded to the nearest hundredth milliliter and the difference between the initial and final volumes was calculat... ... middle of paper ... ...itial and final volumes was calculated; 31.35 mL or 0.03135 L. This volume in liters was multiplied by the concentration of the NaOH solution, 0.2838 M to determine the number of moles of acetic acid solution. This value was then divided by the volume of acetic acid solution originally added to the flask, 10.00 mL or 0.01 L, to obtain the molarity of the acetic acid solution; 0.8903 M. This process was replicated exactly a second and third time. The second titration required 31.39 mL of NaOH to be added, resulting in an acetic acid molarity of 0.8915 M. The third titration required 31.44 mL of NaOH to be added, resulting in a molarity of 0.8929 M. The values obtained for the molarity of the acetic acid solution, since they were close enough to each other in value, were averaged together to obtain 0.8916 M, the calculated average molarity of the acetic acid solution.
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