World Journal of Chemical Education
ISSN (Print): 2375-1665 ISSN (Online): 2375-1657 Website: http://www.sciepub.com/journal/wjce Editor-in-chief: Prof. V. Jagannadham
Open Access
Journal Browser
Go
World Journal of Chemical Education. 2017, 5(6), 193-196
DOI: 10.12691/wjce-5-6-1
Open AccessArticle

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

Chad Rezsnyak1,

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

Pub. Date: November 18, 2017

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

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.

Keywords:
first-year undergraduate/general laboratory instruction hands-on learning equilibrium thermodynamics

Creative CommonsThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

References:

[1]  Holme, T.; Murphy, K., The ACS Exams Institute Undergraduate Chemistry Anchoring Concepts Content Map I: General Chemistry. Journal of Chemical Education 2012, 89 (6), 721-723.
 
[2]  Brown, T. L.; LeMay, H. E.; Bursten, B.; Murphy, C.; Woodward, P. M., Chemistry: The Central Science. 12th ed.; Pearson Prentice Hall: 2012.
 
[3]  Burdge, J.; Overby, J., Chemistry Atoms First. 2nd ed.; McGraw-Hill: 2014.
 
[4]  Zumdahl, S. S.; Zumdahl, S. A., Chemistry: An Atoms First Approach. 2nd ed.; Cengage Learning: 2016.
 
[5]  Antony, E.; Muccianti, C.; Vogel, T., An Experimental Determination of Thermodynamic Values. Journal of Chemical Education 2012, 89 (4), 533-535.
 
[6]  Ben-Dor, L.; Marcus, Y., The Octahedral-Square-Planar Transition of Nickel Chelates. Journal of Chemical Education 1998, 75 (11), 1458.
 
[7]  Euler, W. B.; Kirschenbaum, L. J.; Ruekberg, B., Determination of Ksp, G0, H0, and S0. Journal of Chemical Education 2000, 77 (8), 1039.
 
[8]  Junquera, E.; Aicart, E., An Easy and Fast Experiment for the Determination of the Equilibrium Constants of an Acid-Base Pair, Free and Complexed with a Molecular Receptor. 2000, 77 (9), 1215.
 
[9]  Kendrow, C.; Baum, J. C.; Marzzacco, C. J., Investigating the Thermodynamics of Charge-Transfer Complexes. A Physical Chemistry Experiment. 2009, 86 (11), 1330.
 
[10]  Koga, N.; Shigedomi, K.; Kimura, T.; Tatsuoka, T.; Mishima, S., Neutralization and Acid Dissociation of Hydrogen Carbonate Ion: A Thermochemical Approach. Journal of Chemical Education 2013, 90 (5), 637-641.
 
[11]  Lindquist, D.; Mackin, J.; Nyasulu, F. W.; Cusworth, W., Flame Emission Spectrometry in General Chemistry Labs: Solubility Product (Ksp) of Potassium Hydrogen Phthalate. 2007, 84 (3), 456.
 
[12]  Nyasulu, F.; Nething, D.; Barlag, R.; Wise, L.; Arthasery, P., Thermodynamics of the [CoCl(iPrOH)3]+ to [CoCl(iPrOH)2(MeOH)3]+ Reaction: A General Chemistry Laboratory Exercise. Journal of Chemical Education 2012, 89 (4), 536-539.
 
[13]  Neidig, H. A.; Yingling, R. T., Thermodynamics of the ionization of acetic and chloroacetic acids. Journal of chemical education 1965, 42 (9), 484-5.
 
[14]  Miessler, G. L.; Tarr, D. A., Inorganic Chemistry. 3rd ed.; Pearson Prentice Hall: 2004.