The relationship between the cohesive energy density, the internal pressure, and the surface tension of ionic liquids Yizhak Marcus1; 1HEBREW UNIVERSITY, Jerusalem, Israel; PAPER: 17/Molten/Regular (Oral) SCHEDULED: 17:10/Thu. 24 Oct. 2019/Ambrosia A (77/RF) ABSTRACT: The balance between the attractive and repulsive forces between the ions in room temperature ionic liquids (RTILs) and their high-melting molten salts (MSs) analogs is responsible for their cohesive energy density (ced), their internal pressures (P<sub>int</sub>) and their surface tensions (σ). Therefore, definite relationships exist between these quantities pertaining to the ionic liquids. For 33 RTILs and 53 MSs for which all the data are available, the relationships are linear and take the form ced = a + b(σV<sup>-1/3</sup>) and P<sub>int </sub>= p + q(σV<sup>-1/3</sup>). The quantity σV<sup>-1/3</sup>, called the Gordon parameter, has the dimension of a pressure, as do ced and Pint. The slopes b ≈ 67 and q ≈ 25 are the same for these two kinds of ionic liquids, because the electrostatic interactions between the ions are the dominant attractive forces. The internal energy of the ionic liquid is inversely proportional not to its volume, but to a higher power of it, so that the cohesive (or internal) energy divided by the volume (the ced) is more than twice its volume derivative (the internal pressure, P<sub>int</sub>). The established relationships can help estimate unknown quantities among the three dealt with here from the other two. References: Y. Marcus: The internal pressure and cohesive energy density of liquid metallic elements. Int. J. Thermophys. 38, 1-9 (2016). Y. Marcus: The internal pressure and cohesive energy density of two inorganic liquids: bromine and carbon disulfide. J. Chem. Thermodyn., 98, 317-318 (2016). Y. Marcus: Relationships between the internal pressure, the cohesive energy and the surface tension of liquids. Phys. Chem. Liq., 55, 522-531 (2017). Y. Marcus: The structure of mixtures of water and methanol derived from their cohesive energy densities and internal pressures at 298 to 473 K. J. Phys. Chem B, 121, 863-866 (2017) |