ИСТИНА

This work is a part of systematic study of the thermodynamic properties of ionic liquids by classical thermochemical methods: low-temperature vacuum adiabatic calorimetry and dissolution calorimetry. The object of this study is 1-butyl-3-methylimidazolium methanesulfonate (BmimMS). The aim of the work is to determine the low-temperature heat capacity over a wide temperature range and to calculate the standard thermodynamic functions of the BmimMS formation in the crystal and liquid states. The isobaric heat capacity of the crystal and liquid phases of BmimMS was determined in the temperature range from 80 to 380 K by the vacuum adiabatic calorimetry. There are no phase transition exept melting at 349.13 ± 0.2 K on the heat capacity curve of BmimMS (Figure 1). Melting parameters were also refined by DSC. At temperatures from 5 to 80 K the heat capacity of BmimMS was assessed by the Kelly method. The temperature dependencies of BmimMS main thermodynamic functions have been determined in the temperature range from 5 to 380 K (isobaric heat capacity Cp,m(T), standard entropy S 0m(T), heat content H 0 (T) ‒ H 0 (0), Gibbs energy content G 0 (T) ‒ H 0 (0)). The BmimMS enthalpy of formation at 298.15 K was previously determined by the dissolution calorimetry [1]. In the present study the standard entropies and Gibbs energies of BmimMS formation in the crystal and liquid state at 298.15 K were calculated from the experimental data of adiabatic calorimetry in conjunction with dissolution calorimetry data. Comparison of the obtained thermodynamic characteristics with the literature data was carried out. [1] L.A. Tiflova, D.A. Kalinyuk , A.I. Druzhinina, Book of abstracts of XXIII International Conference on Chemical Thermodynamics in Russia, 2022, 86. Investigation was supported by the Program “Chemical Thermodynamics and Theoretical Material Science” (AAA-1210313000391) and by the Federal Project "Growth of Advanced Infrastructure for Research and Development in the Russian Federation" of the national project "Science and Universities" (updating of equipment for scientific research).