Spectrophotometric measurement of the first dissociation constants of carbonic acid at elevated temperatures

Abstract

Using 2,5-dintrophenol as an optical indicator, the pH of a carbonate buffer solution was spectrophotometrically measured at temperatures from 25 to 175°C. The pH values measured in this study were utilized to determine the first dissociation constant of carbonic acid at various temperatures. The result was

where T is in Kelvin. By using this fitted function, the thermodynamic functions for carbonic acid at 25°C were calculated. When the dissociation reaction of carbonic acid was rewritten as an isocoulombic reaction, the plot of log K_OH against 1/T was approximately linear over the temperature ranges studied, as in other isocoulombic reactions.

References

1. H. S. Harned and R. Davis Jr., J. Am. Chem. Soc., 1943, 65, 2030.
2. R. N. Roy, J. J. Gibbons, M. D. Wood, R. W. Williams, J. C. Peiper and K. S. Pitzer, J. Chem. Thermodyn., 1983, 15, 37.
3. C. S. Patterson, G. H. Slocum, R. H. Busey and R. E. Mesmer, Geochim. Cosmochim. Acta, 1982, 46, 1653.
4. T. Shedlovsky and D. A. McInnes, J. Am. Chem. Soc., 1935, 57, 1705.
5. A. J. Ellis, J. Chem. Soc., 1959, 3689.
6. A. J. Read, J. Solution Chem., 1975, 4, 53.
7. Y. S. Huh, J. G. Lee, D. C. McPhail and K. Kim, J. Solution Chem., 1993, 22, 615.
8. I. J. Lee, G. S. Jung and K. Kim, J. Solution Chem., 1994, 23, 1283.
9. T. W. Shin, K. Kim and I. J. Lee, J. Solution Chem., 1997, 26, 379.
10. M. H. Kim, C. S. Kim, H. W. Lee and K. Kim, J. Chem. Soc., Faraday Trans., 1996, 92, 4951.
11. H. J. Kweon, J. T. Cheong and K. Kim, New Phys., (Korean Phys. Soc.), 1990, 30, 570.
12. R. Wiebe and V. L. Gaddy, J. Am. Chem. Soc., 1940, 62, 815.
13. R. Wiebe and V. L. Gaddy, J. Am. Chem. Soc., 1941, 63, 475.
14. A. J. Ellis, Am. J. Sci., 1959, 257, 217.
15. A. Zawisza and B. Malesinsky, J. Chem. Eng. Data, 1981, 388.
16. A. J. Ellis and R. M. Golding, Am. J. Sci., 1963, 47, 261.
17. H. R. Corti, J. J. de Pablo and J. M. Prausnitz, J. Phys. Chem., 1990, 94, 7876.
18. L. N. Plummer and E. Busenberg, Geochim. Cosmochim. Acta, 1982, 46, 1011.
19. P. Scharlin, in IUPAC Solubility Data Series, ed P. Scharlin, Oxford University Press, Oxford, vol. 62, 1996.
20. F. M. M. Morel and J. G. Hering, Principles and Applications of Aquatic Chemistry, Wiley, New York, 1993, p. 61.
21. H. C. Helgeson and D. H. Kirkham, Am. J. Sci., 1974, 274, 1199.
22. H. R. Corti and R. J. Fernandez-Prini, High-Temperature Aqueous Solutions: Thermodynamic Properties, CRC Press, Boca Raton, FL, 1992.