The purpose of this lab was to analyze commercial aspirin tablets. To do so, the percent acetylsalicyclic acid (active ingredient) in tablets using acid-base titration was determined, the percent acetylsalicyclic acid in tablets by formation of a colored iron(III)-salicylate complex was determined using spectrometry, and then the percents from each process was compared. Acetylsalicylic acid is produced when salicylic acid and acetic anhydride react in the presence of H2SO4. Consequently, the said reaction produces acetylsalicylic acid and acetic acid. In part one of the lab, titration of a NaOH solution with an indicator and a known concentration into a solution containing a specific amount of Member’s Mark aspirin occurred. Using the balanced equation C9H8O4 + NaOH NaC9H7O4 + H2O, the percent concentration of acetylsalicyclic acid was determined. In part two of the lab, six dilutions of a standard acetylsalicyclic acid were produced and analyzed using a spectrophotometer to determine the maximum absorbance of an iron(III) salicylate complex. Using identical methods, an additional solution was created using Member’s Mark aspirin instead of acetylsalicyclic acid. The resulting concentration of acid was then calculated using the prepared standard curve (made during the original six dilutions), readings from the spectrophotometer, and Beer’s Law. Results:
In part one of the lab, the mass percent of acetylsalicyclic acid within Member’s Mark aspirin was determined through acid-base titration. Table 1. Mass Percent of Acetylsalicylic Acid in Member’s Mark Aspirin | Mass of Tablet| Volume NaOH Delivered| Moles NaOH Delivered| Moles Acid in Tablet| Mass of Acid in Tablet| Mass Percent| Run 1| .6498g| 23.29mL| .0018 mols| .0018 mols| 324mg| 85.7%| Run 2| .6507g| 23.83mL| .0018 mols| .0018 mols| 324mg| 85.3%| Average| | | | | 324mg| 85.5%|
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