Revisiting the Determination of Percent Aspirin Lab: Using a Limiting Reactant Approach for Students To Also Determine the Amount of Iron(III) Chloride

The spectrophotometric determination of the percent composition of an aspirin tablet is a common first-year, general chemistry undergraduate laboratory procedure. The experiment requires that a known amount of pure acetylsalicylic acid be quantitatively converted into the soluble disodium salicylic...

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Bibliographic Details
Published in:Journal of chemical education 2020-02, Vol.97 (2), p.574-577
Main Authors: Bodek, Matthew, Burch, Mary, Cannon, Joshua, Finneran, David, Geveke, Kathleen, Sinkinson, Heather, Smith, William, Tierney, John
Format: Article
Language:English
Subjects:
Acetylsalicylic acid
Aspirin
Chemistry
College students
Complexity
Ferric chloride
Hands on Science
Iron chlorides
Laboratories
Laboratory Experiments
Organic chemistry
Pharmacology
Salicylic acid
Science Experiments
Secondary school students
Spectrophotometry
Spectroscopy
Students
Teaching methods
Undergraduate Students
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Summary:The spectrophotometric determination of the percent composition of an aspirin tablet is a common first-year, general chemistry undergraduate laboratory procedure. The experiment requires that a known amount of pure acetylsalicylic acid be quantitatively converted into the soluble disodium salicylic acid that is further reacted with excess iron­(III) chloride solution to form a deep blue tetraaqua-octahedral complex. This complex, through serial dilutions, is used to construct a Beer’s law plot that may be used to determine the concentration of aspirin. In a novel twist, this paper describes how the same Beer’s law plot can be used to determine the concentration of iron in the iron­(III) complex, which is then used to determine the concentration of the original iron­(III) chloride solution used to make the aspirin–iron­(III) complex. The method has been adapted by high school students in determining iron concentrations in stream waters.
ISSN:0021-9584
1938-1328
DOI:10.1021/acs.jchemed.9b00154