Standard Absolute Entropy, , Values from Volume or Density. 1. Inorganic Materials

Abstract

Standard absolute entropies of many inorganic materials are unknown; this precludes a full understanding of their thermodynamic stabilities. It is shown here that formula unit volume, V(m)(), can be employed for the general estimation of standard entropy, S degrees 298 values for inorganic materials of varying stoichiometry (including minerals), through a simple linear correlation between entropy and molar volume. V(m)() can be obtained from a number of possible sources, or alternatively density, rho, may be used as the source of data. The approach can also be extended to estimate entropies for hypothesized materials. The regression lines pass close to the origin, with the following formulas: For inorganic ionic salts, S degrees 298 /J K(-)(1) mol(-)(1) = 1360 (V(m)()/nm(3) formula unit(-)(1)) + 15 or = 2.258 [M/(rho/g cm(-)(3))] + 15. For ionic hydrates, S degrees 298 /J K(-)(1) mol(-)(1) = 1579 (V(m)()/nm(3) formula unit(-)(1)) + 6 or = 2.621 [M/(rho/g cm(-)(3))] + 6. For minerals, S degrees 298 /J K(-)(1) mol(-)(1) = 1262 (V(m)()/nm(3) formula unit(-)(1)) + 13 or = 2.095 [M/(rho/g cm(-)(3))] + 13. Coupled with our published procedures, which relate volume to other thermodynamic properties via lattice energy, the correlation reported here complements our development of a predictive approach to thermodynamics and ultimately permits the estimation of Gibbs energy data. Our procedures are simple, robust, and reliable and can be used by specialists and nonspecialists alike.

Calorimetric Determination of Heat Capacity, Entropy and Enthalpy of Mixed Oxides in the System CaO–SrO–Bi2O3–Nb2O5–Ta2O5

“…A linear correlation between the standard molar entropy at 298.15 K and the formula unit volume Vf.u has been proposed by Jenkins and Glaser [54][55][56]. This approach was used in this work for mixed oxides in the CaO-SrO-Bi2O3-Nb2O5-Ta2O5 system.…”

Establishing Consistent van der Waals Volumes of Polyatomic Ions from Crystal Structures

“…[1,2] In particular, the prediction of thermodynamic properties for condensed phases based on volume has gained high popularity. [3,4] The volume-based thermodynamics (VBT) approach has been proven to predict the lattice enthalpy, [3,5] lattice entropy, [5,6] heat capacity [7] and so forth of ionic compounds. The VBT approach has been successfully transferred to the description and prediction of several physical properties of ionic liquids (ILs).…”

NMR Spectroscopic Evidence for the Intermediacy of XeF3− in XeF2/F− Exchange, Attempted Syntheses and Thermochemistry of XeF3− Salts, and Theoretical Studies of the XeF3− Anion

“…The current study also clarifies inconsistencies that have arisen in recent computational studies relating to the structure of the XeF3 -anion. [25][26][27][28][29] were used in conjunction with known thermodynamic quantities to estimate Hºrxn, Sºrxn, and Gºrxn for eq 1 in the absence of a solvent. The standard enthalpies for the reactions were determined by analyzing their Born-Fajans-Haber cycles (eq 2).…”