Ideal solutions cohesion energies

The interactions between molecules which produce the cohesive energy characteristic of the liquid phase are described in the section entitled Secondary Forces Between Solvent and Solute Molecules. These involve the dispersion forces, dipole-dipole and dipole-induced dipole interactions, and specific interactions, especially hydrogen bonding. If it is assumed that the intermolecular forces are the same in the vapor and liquid states, then -E is the energy of a liquid relative to its ideal vapor at the same temperature. It can be described as the energy required to vaporize 1 mole of liquid to the saturated vapor phase (Af U) plus the energy required for the isothermal expansion of the saturated vapor to infinite volume. Detailed discussion of the theory and derivations is given in the publications by Hildebrand and associates cited above. 

As a result, the cohesive energy is the enthalpy of evaporation plus the change in enthalpy to expand from the vapor pressure to the ideal gas state (which is usually neglected in liquids at ordinary temperatures and low pressures, see also Section 4.2.1) minus RT. The cohesive energy concept is used to derive regular solution theory and also the solubility parameters (see Section 5.3). 

Athermal transformation n. A reaction that proceeds without thermal (not dependent on heat, enthalpy AH = 0) activation as contrasted to isothermal transformation, which occurs at constant temperature. An athermal mixture of liquids or polymer in a solvent involves no enthalpy AH = 0) change in an ideal solution and the Gibbs free energy (—AG) is always negative for the solution (polymer dissolved in solvent) to occur while the entropy (AS) increases. Barton AFM (1983) Handbook of solubility parameters and other cohesion parameters. CRC Press, Boca Raton. 

Ideal solution n. Solutions that exhibit no change of internal energy on mixing and complete uniformity of cohesive forces. The behavior of ideal solutions is described by Raoult s law over all ranges of temperature and concentration. 

---