Hygrometric Determination of Water Activities and Osmotic and Activity Coefficients of NH4Cl–KCl–H2O at 25°C |
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Authors: | Abderrahim Dinane Abdelfetah Mounir |
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Institution: | (1) Ecole Royale Navale, Département Universitaire, Boulevard Sour Jdid, Casablanca, Maroc;(2) Laboratoire de Chimie Physique, Département de Chimie, Faculté des Sciences Ben M'sik, Université Hassan II Mohammedia, B.P 7955, Casablanca Maroc |
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Abstract: | Relative humidities have been measured for mixed aqueous electrolyte system of ammonium and potassium chlorides by the hygrometric method at total molalities from 0.3 to 6 mol-kg–1for ionic-strength fractions yof NH4Cl of 1/3, 1/2, and 2/3 at 25°C. The data allow the calculation of new water activities and osmotic coefficients. The proposed ECA (extended composed additivity) rule of calculation of water activity in mixed aqueous electrolyte solutions from the water activities of a single component is extended to this system. The experimental results and the predictions of the ECA rule are compared with the Robinson–Stokes, Reilly–Wood–Robinson, the Pitzer, and the Lietzke–Stoughton II models. Predictions made using these models are, in general, consistent with our results. From these measurements, the Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture for different ionic-strength fractions. |
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Keywords: | Aqueous mixed electrolyte ammonium and potassium chloride relative humidity water activity osmotic coefficient activity coefficient Pitzer's model ECA rule |
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