Sublimation Gibbs energy

Fig. 1. Standard Gibbs energy of formation vs temperature where changes in state are denoted as M, B, and S for melting, boiling, and sublimation points.

Define M/M+ = — AGsub — Im + AGg0l AGsub is the Gibbs energy of sublimation. 

R.B. Cundall et al, "Vapor Pressure Measurements on Some Organic High Explosives , J-ChemSoc, Faraday Trans I, 74 (6), 1339—45 (1978) CA 89, 181933 (1978) [Equilibrium vap press were detd for various expls by the Knudson cell technique. The data for HMX follows the Clausius-Clapeyron eqtn. The values detd for the const A and B in the eqtn, log10p = A—(B/T), plus the std enthalpy, entropy and Gibbs energy of sublimation from the authors calcns are presented in Table 7 ... 

By introducing this scale, we can separate the total emf of the cell into two quantities, for which the contributions (AGsubi, AGion, and AG are the sublimation, ionization, and real hydration -> Gibbs energies, respectively) can be experimentally determined. For the -> hydrogen electrode it holds that... 

The enthalpy of formation of YF3 was determined by Rudzitis, Feder, and Hubbard 164) using fluorine bomb calorimetry. NdCla was done by solution methods (179), and the enthalpies of formation of LaFs and PrFa were determined by Polyachenok 161) who employed an indirect equilibration technique. A recent torsion-effusion study of the vapor pressure of CeFs 115) yields second and third law values for the enthalpy of sublimation. The thermodynamics of the chlorination of rare earths with gaseous chlorine have also been investigated 144). Gibbs energies of formation were determined for CeClg by solid-state electromotive force techniques 41). 

K regardless of its stability. For example, if the vapor pressure over liquid copper is analyzed using Cu(/) Gibbs energy functions, the result is the enthalpy of vaporization of the liquid at 298.15 K. To calculate the enthalpy of sublimation of Cu(cr) it is necessary to add the enthalpy of fusion at... 

The enthalpy of sublimation at 298.15 K was obtained from the difference in the enthalpy of formation of the gas and solid at 298.15 K. The sublimation point was obtained from the Gibbs energy crossover between gas and solid at one bar. 

The sublimation point is calculated from the Gibbs energy crossover between crystal and gas. However, it should be noted that MoClg(cr) is unstable with respect to MoClg(cr) at all temperatures and thus sublimation could occur only under an atmosphere of Clg. 

The boiling point is calculated from the adopted thermodynamic functions and the chosen enthalpy of sublimation at 298.15 K so that the Gibbs energy functions calculated by integration of the crystal liquid data and by statistical methods from the gas phase are equal at the boiling point. 

Sublimation with decomposition to Hg(g) and HgFgCg) Is assumed at 949 K from the Gibbs energy change of the reaction. 

The value of Ag H (298.15 K) was derived from the vapor pressure data by both the 2nd and 3rd law analyses. See the 4 10 table for details. T is the temperature at which the Gibbs energy change of the reaction P 0jQ(hex, cr) = 40 0 approaches zero. Sublimation temperature for P OjQ(cr) was derived to be 632 K, 636 K (average of three determinations) and 623.7 K (average of two determinations) by Frandsen (6) from the vapor pressure data reported by Hoeflake and Scheffer (T), Smits (IB) and Smits and Rutgers (9), respectively. 

Chemical processes are denoted by the operator A, written before the symbol for a property, as recommended by lUPAC [82LAF]. An exception to this rule is the equilibrium constant, cf. Section II. 1.6. The nature of the process is denoted by annotation of the A, e.g., the Gibbs energy of formation, AfG, the enthalpy of sublimation,, etc. 

The Gibbs energy of an atom in the kink position (chemical potential) can be derived from the sublimation enthalpy (Vohner ) a discussion is also found in the book of Budevski, Staikov and Lorenz. ... 

Hougen et discuss the estimation of thermodynamic properties from molecular structure data. Gambill, in numerous articles to be found in the four volumes listed, deals with methods for the prediction of heat capacities of liquids and gases, enthalpies of vaporization, fusion and sublimation, critical temperature and pressure, and p, K, T data, including liquid densities. Dasent < presents methods for the estimation of the standard Gibbs energy of formation of non-existent compounds and compounds of low stability by procedures based on the use of ionic and covalent models. 

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