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					                                                            Properties of Aspirin
                                                            Lab 38


Purpose-
        The objective of the lab was to determine experimentally the physical properties
of aspirin and its chemical properties.

Procedure-
      We followed the procedure in the lab book.

Results
          Solubility Tests:
                 Solvent                  Salicylic Acid           Aspirin
                 Methanol                 soluble                  slightly soluble
                 Toluene                 slightly soluble          insoluble
                 Cold water              insoluble                 slightly soluble
                 Hot water               insoluble                 slightly soluble
          Functional Groups:
                 Test Reagent
                 FeCl3                   turned purple             aspirin dissolved
                 NaHCO3                  became soluable           bubbles formed

                                          Trial 1                  Trial 2
Discussion
        In this lab we examined the properties of normal household aspirin tablets
(acetylsalicylic acid) through the titration and calculation of pH levels using a pH meter.
By determining the pH with the pH meter, the pKa and Ka can be calculated. After such
calculations, the molecular mass of aspirin can be obtained by dividing the moles of
aspirin used into the grams of aspirin used. This lab is an example of how pH and the
acidity constant (Ka) can be used to not only determine molecular mass of a substance,
but also the chemical structural formula of a substance (acetylsalicylic acid C9H8O4). We
also performed solubility tests in order to determine the solubility of salicylic acid and
aspirin methanol, toluene, cold water, and warm water. Finally we added test reagents to
these solutions and recorded the effect that each had on the aspirin and salicylic acid
solutions.

Questions
        1. The evidence that the aspirin tablets are not pure acetylsalicylic acid lies in the
fact that the aspirin tablets were not soluble in water when we performed the solubility
tests.
        2. The affect that an 85% pure tablet would have on the molecular mass would be
that the derived molecular mass from experimentation would be higher because other
substances in the tablet might account for some changes in the pH in the titration.
        3. Because there may be other substances in the tablet that would effect the pH of
the solution being titrated, there may be an increase in the Ka value for the aspirin.

				
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