Visualization of Validity Ranges for Acid Approximations: Error Contour Plots as a Function of Concentration and K<inf>a</inf>
Issued Date
2023-01-01
Resource Type
ISSN
00219584
eISSN
19381328
Scopus ID
2-s2.0-85178612846
Journal Title
Journal of Chemical Education
Rights Holder(s)
SCOPUS
Bibliographic Citation
Journal of Chemical Education (2023)
Suggested Citation
Limpanuparb T., Ho J. Visualization of Validity Ranges for Acid Approximations: Error Contour Plots as a Function of Concentration and K<inf>a</inf>. Journal of Chemical Education (2023). doi:10.1021/acs.jchemed.3c00751 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/91453
Title
Visualization of Validity Ranges for Acid Approximations: Error Contour Plots as a Function of Concentration and K<inf>a</inf>
Author(s)
Author's Affiliation
Other Contributor(s)
Abstract
Approximate mathematical treatments are commonly taught in undergraduate chemistry, but the validity ranges of these approximations have rarely been properly defined. We present error contour plots of commonly used quadratic approximations for calculating equilibrium proton concentrations of monoprotic acids. Students and instructors can easily read these plots to estimate the error in their approximation of proton concentration (1%, 5%, 10%, and 25%) at a given initial acid concentration [HA]0 and dissociation constant Ka value. In addition, we introduce a new quadratic expression which will always deliver an error no larger than 25% (or 0.1 pH unit) in ideal solution irrespective of the acid strength and concentration. These results extend readily to their analogue of pOH, Kb, and [A-] for bases. Our novel approach here could significantly reduce many different situations students must master into one that can be computed straightforwardly without caveats or conditions.