As part of a departmental initiative to incorporate Raman spectroscopy throughout the undergraduate chemistry curriculum, we have developed a laboratory experiment in the second semester General Chemistry course that focuses on the acidic properties of solutions of nitric acid. Students obtain Raman spectra of nitric acid in sealed tubes with concentrations ranging from 1 -16 M. At low concentrations (&lt; 5 M), Raman bands associated with free nitrate ions are primarily observed, consistent with the strong acid properties of nitric acid. However, at concentrations above 5 M, bands associated with undissociated nitric acid begin to appear and increase in intensity at higher concentrations. Students are challenged to explain these results using strict application of Bronsted-Lowry theory, which leads them to the conclusion that nitric acid does not always act as a strong acid according to the strict definition (100% dissociated in aqueous solution). Comparison of students who performed this experiment with a control group that did not, shows superior performance on content and critical thinking assessments for the experimental group. Implications of this experiment on the teaching of acid-base theory will be discussed.<br/>

Nitric acid as a weak acid:  Interpreting evidence from Raman spectroscopy

255th National Meeting (2018)

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