Heat Capacity of Alcoholic (Isopropyl Alcohol) and Aqueous Alcoholic Solutions of Sodium Iodide Electrolyte Salt as a Function of Concentration

The paper considers using a high-sensitivity calorimeter with an isothermal jacket to measure heat capacities of electrolyte salt solutions at the temperature of 298.15 K, the salt being sodium iodide NaI dissolved in isopropyl alcohol and in mixtures of isopropyl alcohol with water containing 10, 20, and 40 % water by mass, at various molalities of the electrolyte salt. We processed the apparent heat capacity values computed for the electrolyte salt by means of the ion association model, which assumes that there exists an equilibrium between ions and ion pairs of the same type in a solution. The association constant values obtained make it possible to predict the heat capacity values not measured empirically, which lie within the margin of error of the experimental values. The investigation shows that the apparent heat capacity of the electrolyte salt as a function of concentration is adequately described by the ion association model in a wide range of solution molalities

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