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Selection of chemical conductivity model in the study of ion-association reaction

In this paper conductometric experimental data were processed using chemical models based on well-known equations Fuoss-Hsia, Lee-Wheaton and Pitts. These equations were derived from different ionic models and derived with various mathematical approximations so their accuracy and reliability was estimated by applying the same conductometric data. The models were compared and evaluated based on the results and their deviations from the experimental points as well as by obtained standard thermodynamic quantities of the association reaction. A three – parameter adjustment usually fails to provide uniform values for the association distance R [1]. So it is not possible to know the size and nature of the ion pair. Therefore, three fixed values for this parameter were chosen: R = a (a is the sum of the crystallographic radii), R = a + d (d is the diameter of the solvent molecule) and R = q (q is the Bjerrum critical distance) [2]. By repeated calculation three solutions for Λo and KA were obtained at each temperature, and three sets of thermodynamic quantities of the association reaction were derived at 298, 15 K. The most acceptable results are those that lead to the best agreement between the models. The best agreement between the models regarding all above mentioned quantities is obtained when R = q.

Conductivity model, ion-association reaction

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