Abstract
The apparent first ionization constant of carbonic acid has been determined by conductivity measurements and found to vary from 4.32×10−7 at 25°C to 1.6×10−8 at 250°C. The pressure effect to 2000 bar has been measured, and the ratio Kp/K1 is 7.3 at 25°C and 19 at 250°C. The standard partial molar volume change for the ionization at 1 bar,\(\Delta \bar V_1^0\), increases from −27.6 cm3-mole−1 at 25°C to −88 cm3-mole−1 at 250°C. The volume changes are smaller at higher pressures. A linear correlation between\(\Delta \bar V_1^0\) and the partial molar compressibility for the ionization reaction has been noted. A similar correlation exists between the partial molar entropy and volume changes for the reaction.
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Read, A.J. The first lonization constant of carbonic acid from 25 to 250°C and to 2000 bar. J Solution Chem 4, 53–70 (1975). https://doi.org/10.1007/BF00646052
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DOI: https://doi.org/10.1007/BF00646052