Abstract
The equilibrium constant for the disproportionation of iodine in aqueous solution was determined as a function of temperature from 3.8 to 209.0°C using emf measurements in low ionic strength media. The equilibrium constant and associated molal thermodynamic quantities at 25°C are: K1=1.17±0.62×10−47, ΔHo=273±3 kJ-mol−1, ΔSo=16±9 J-K−1-mol−1, and ΔC op =−1802±41 J-K−1-mol−1. Although the value of K1 is in excellent agreement with a previous emf measurement at 25°C, these results conflict with the corresponding parameters obtained from the NBS tables. Moreover, at temperatures above ca. 100°C, our measured values for the equilibrium constant diverge strongly from all previous estimates and predictions.
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Palmer, D.A., Ramette, R.W. & Mesmer, R.E. Potentiometric studies of the thermodynamics of iodine disproportionation from 4 to 209°C. J Solution Chem 13, 685–697 (1984). https://doi.org/10.1007/BF00649009
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DOI: https://doi.org/10.1007/BF00649009