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

Authors: Akhapkina T.E., Gurov A.A., Solovev S.N., Kozhevnikova S.V. Published: 03.11.2021
Published in issue: #5(98)/2021  
DOI: 10.18698/1812-3368-2021-5-109-124

 
Category: Chemistry | Chapter: Physical Chemistry  
Keywords: apparent heat capacity of electrolyte, ion association model, association constant, heat capacity 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

References

[1] Solovyev S.N. Ion association and the concentration dependence of the heat capacities of electrolyte solutions. Russ. J. Phys. Chem., 1998, vol. 72, no. 9, pp. 1466--1468.

[2] Solovyev S.N., Khekalo T.V. Opredelenie termodinamicheskikh kharakteristik assotsiatsii elektrolitov v rastvore na osnove termokhimicheskikh izmereniy [Definition of thermodynamic characteristics electrolyte association in solutions on thermochemical data]. Trudy MKhTI im. D.I. Mendeleeva [Proceedings of Mendeleev UCTR], 1989, iss. 158, pp. 129--138 (in Russ.).

[3] Khekalo T.V. Termodinamicheskie kharakteristiki assotsiatsii ionov v nevodnykh i smeshannykh rastvorakh galogenidov shchelochnykh metallov i tetra-n-butilammoniya po dannym termokhimicheskikh izmereniy. Avtoreferat dis. kand. khim. nauk [Thermodynamic characteristics of ion association in non-aqueous and mixed solutions of alkali halide and tetra-n-butylammonium according to thermochemical measurements. Abs. Cand. Sc. Chem. Diss.]. Moscow, MUCTR Publ., 1990 (in Russ.).

[4] Kolesov V.P. Osnovy termokhimii [Basics of thermochemistry]. Moscow, Lomonosov MSU Publ., 1996.

[5] Shatalov K.I., Solov’ev S.N. The standard enthalpy of formation of K2[NiF6](cr). Russ. J. Phys. Chem., 2009, vol. 85, iss. 6, pp. 331--333. DOI: https://doi.org/10.1134/S0036024411020312

[6] Akhapkina T.E., Krusheva M.A., Solov’ev S.N., et al. Thermochemistry of С60 fullerene solutions in benzene, toluene, o-xylene, and o-dichlorobenzene at 298.15 K. Russ. J. Phys. Chem., 2017, vol. 91, iss. 2, pp. 301--304. DOI: https://doi.org/10.1134/S0036024417020029

[7] Glushko V.P., ed. Termicheskie konstanty veshchestv. Vyp. 1--10 [Thermal constants of compounds. Iss. 1--10]. Moscow, VINITI Publ., 1965--1981 (in Russ.).

[8] Novikov A.N. Praktikum po khimicheskoy termodinamike rastvorov [Tutorial on solution chemical thermodynamics]. Novomoskovsk, MUCTR Publ., 2018.

[9] Vasilev V.A. Raschet plotnosti i teploemkosti vodnykh rastvorov neorganicheskikh soedineniy [Calculation of density and heat capacity water solutions of inorganic compounds]. Moscow, MUCTR Publ., 1979.

[10] Cox J.D., Wagman D.D., Medvedev V.A. CODATA key values for thermodynamics. Hemisphere, 1989.

[11] Belousov V.P., Morachevskiy A.G., Panov M.Yu. Teplovye svoystva rastvorov neelektrolitov [Thermal properties of nonelectrolyte solutions]. Leningrad, Khimiya Publ., 1981.

[12] Krachkovskaya Yu.A., Ovchinnikova O.V., Solovyev S.N. Equation for calculating heat capacity of electrolyte solutions submitting to the theory of Debye --- Huckel. Trudy MKhTI im. D.I. Mendeleeva [Proceedings of Mendeleev UCTR], 2014, iss. 187, pp. 124--131 (in Russ.).

[13] Solov’ev S.N., Senatorova S.V., Kolesnik E.A. A new equation for calculating the enthalpies of dilution of solutions of nonassociated electrolytes. Russ. J. Phys. Chem., 2006, vol. 80, iss. 10, pp. 1683--1685. DOI: https://doi.org/10.1134/S0036024406100244

[14] Kuznetsova E.M. Quantitative description thermodynamic properties individual and mixed strong electrolyte solutions in different solvents in wide range of concentrations. Zhurn. fiz. khimii, 1983, vol. 57, no. 9, pp. 1765--1775 (in Russ.).

[15] Akhapkina T.E., Gurov A.A., Solovev S.N., et al. An equation for computing thermal capacity of an electrolyte in a dissociated solution. Herald of the Bauman Moscow State Technical University, Series Natural Sciences, 2019, no. 1 (86), pp. 77--87 (in Russ.). DOI: http://doi.org/10.18698/1812-3368-2019-1-77-87