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Brown, T. L.; LeMay, H. E.; Bursten, B.; Murphy, C.; Woodward, P. M., Chemistry: The Central Science. 12th ed.; Pearson Prentice Hall: 2012.

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Article

Determination of Thermodynamic Values (∆S°, ∆H°, and ∆G°) from the Dissociation of a Weak Acid

1Department of Chemistry, Tennessee Technological University, Cookeville, TN, United States


World Journal of Chemical Education. 2017, Vol. 5 No. 6, 193-196
DOI: 10.12691/wjce-5-6-1
Copyright © 2017 Science and Education Publishing

Cite this paper:
Chad Rezsnyak. Determination of Thermodynamic Values (∆S°, ∆H°, and ∆G°) from the Dissociation of a Weak Acid. World Journal of Chemical Education. 2017; 5(6):193-196. doi: 10.12691/wjce-5-6-1.

Correspondence to: Chad  Rezsnyak, Department of Chemistry, Tennessee Technological University, Cookeville, TN, United States. Email: crezsnyak@tntech.edu

Abstract

The concepts of equilibrium and thermodynamics are among the most important topics covered in a general chemistry course. The thermodynamic properties ∆G°, ∆H°, and ∆S° are difficult to measure directly in a laboratory setting, but can be determined by monitoring the temperature dependence of the equilibrium constant, K. Previously published procedures require sophisticated technology or methodology, such as simultaneously measuring temperature and absorbance using a spectrophotometer, which may be unavailable to small and/or rural colleges and universities. Measuring the pH of a weak acid solution while varying the temperature allows for this analysis to be conducted simply, making it more accessible to broader range of academic laboratories. This experiment outlines the simple measurement of the equilibrium constant and temperature, with aspects of graphical analysis, allowing students to link the concepts of equilibrium and thermodynamics conceptually and mathematically. Calculated values of ∆G°298 are consistent with literature values, indicating that the experiment is suitably robust to be performed successfully by students of a wide range of skill levels.

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