Thermochemical diagram

This condition will cause Reaction 13 to proceed to the right, and Ca(OH)2 will be stable where the CaO is in contact with, the gas phase. We can represent the possible reaction product as a function of gas chemistry in order to construct a thermochemical diagram that depicts the stability range of various condensed phases as functions of the thermodynamic activities of the two components of reactive gas such as CO and H O in air, etc. Based on the above analysis, we can build the thermochemical diagram for CaO and CaC03 and Ca(OH)2 at 500°C by using literature values as a function of pCO and pH O (see Eigure 12). 

Fig. 14. Thermochemical diagram for the Si-O-N system. After Jack [5/]. Reproduced with permission of Kluwer Academic Pubs, Norwell.

Fig. 15. Thermochemical diagram for silicon nitrided at 1200°C showing products of reaction, pressure in atmospheres. After Colquhun et al. 117]. Reproduced with permission of the Institute of Ceramics, Shelton.

Figure 3-6 Thermochemical diagram (Ellingham diagram) of various types of metal.

A number of reviews have appeared covering the various aspects of borate glasses. The stmcture, physical properties, thermochemistry, reactions, phase equihbria, and electrical properties of alkah borate melts and glasses have been presented (73). The apphcation of x-ray diffraction, nmr, Raman scattering, in spectroscopy, and esr to stmctural analysis is available (26). Phase-equihbrium diagrams for a large number of anhydrous borate systems are included in a compilation (145), and thermochemical data on the anhydrous alkah metal borates have been compiled (17). 

Many other parepistemes were stimulated by the new habits of precision in theory. Two important ones are the entropic theory of rubberlike elasticity in polymers, which again reached a degree of maturity in the middle of the century (Treloar 1951), and the calculation of phase diagrams (CALPHAD) on the basis of measurements of thermochemical quantities (heats of reaction, activity coefficients, etc.) here the first serious attempt, for the Ni-Cr Cu system, was done in the Netherlands by Meijering (1957). The early history of CALPHAD has recently been... 

Fig. 7.68 Thermochemical stability diagram for the system Fe-S-O at I 000 K showing the relative corrosion potentials of the atmospheres in conventional coal combustion (A), fluidised bed combustion (B), conventional coal gasification (C) and coal gasificiation using nuclear heat (D) (after Gray and Starr )...

Fig. 7.69 Thermochemical stability diagram for the 310 stainless-steel-S-O system at 750°C (from Gray and Starr after Natesan and Chopra ")...

When the multiplicity of a complex is the same for ionic or ion-dipole bonds and for covalent bonds, the decision as to which extreme bond type is the more closely approached in any actual case must be made with the aid of less straightforward arguments. Sometimes theoretical energy diagrams can be constructed with sufficient accuracy to decide the question. A discussion of crystals based on the Born-Haber thermochemical cycle has been given by Rabinowitsch and Thilo3), and more accurate but less extensive studies have been made by Sherman and Mayer4). 

Critical assessment of phase-diagram data employing the thermodynamics of the phase equilibria in the form of phase-diagram modeling provides consistent thermochemical data (including also the liquid solution) for binary metal-boron systems such as V—B Cr—B, Mn—B, Fe —B, Co—B, Ni—Mo—B and Nb—B, W—B, A1 — B Despite these efforts, reinvestigation of binary systems is... 

Seward (1973) experimentally determined the solubility of Au due to this complex and equilibrium constant for the above reaction. Figure 1.102 shows the solubility of Au on log/oj-pH diagram calculated based on the thermochemical data by Seward (1973). 

From (1-79) it is clear that the Hg content of electrum is related to /sj and A l-vg. Using the thermochemical data for reaction (1-78) by Barton and Skinner (1979), isoactivity lines for Hg in electrum may be drawn on a log/sj-temperature diagram (Fig. 1.175). At a given temperature, the activity of Hg in electrum increases with a decrease in /sj. Therefore, the /sj for the mercurian gold of the Tsugu deposit is inferred to be relatively low. 

Figure 1.175. Activity of S2-temperature diagram showing iso-Hg contents contours for gold. The calculations were carried out using thermochemical data of Craig and Barton (1973).

Iso-FeS content lines for sphalerite in equilibrium with pyrite or pyrrhotite were drawn on the log/sj-temperature diagram (Figs. 1.179 and 1.180) using thermochemical data by Scott and Bames (1971) and Barton and Skinner (1979). 

Previous studies clearly indicated that the chemical compositions of geothermal waters are intimately related both to the hydrothermal alteration mineral assemblages of country rocks and to temperature. Shikazono (1976, 1978a) used a logarithmie cation-Cl concentration diagram to interpret the concentrations of alkali and alkaline earth elements and pH of geothermal waters based on thermochemical equilibrium between hydrothermal solution and alteration minerals. 

Figure 5.2. Potential energy diagrams illustrating the relationships between thermochemical properties, (a) Relationships for properties involving negative ions, and (b) relationships among properties involving positive ions. See Section 2 for definitions.

L. Kaufman, Coupled phase diagrams and thermochemical data for transition metal binary systems-VI, CALPHAD, 3 (1979) 45-76. 

In section 5.1, you learned about the energy changes that accompany physical changes, chemical reactions, and nuclear reactions. You learned how to represent energy changes using thermochemical equations and diagrams. In the next section, you will determine the enthalpy of a reaction by experiment. 

Holdaway M. J. and Mukhopadhyay B. (1993). A reevaluation of the stability relations of andalusite Thermochemical data and phase diagram for the aluminum silicates. Amer Mineral, 78 298-315. 

Thermochemical methods generate lattice stabilities based on high-temperature equilibria that yield self-consistent multi-component phase-diagram calculations. However, as they are largely obtained by extrapolation, this means that in some cases they should only be treated as effective lattice stabilities. Particular difficulties may occur in relation to the liquid — glass transition and instances of mechanical instability. 

Fig. 8 Phase diagram showing the free energy of different surface structures of water at pH = 0 in contact with Au(lll), Pt(lll), and Ni(lll). The lowest line represents the thermochemically most stable phase. The crossing of the two bottom lines indicates a phase change. Reprinted with permission from Rossmeisl et al.. Journal of Physical Chemistry B, 2006, 110, 21833. 2006, American Chemical Society.

Kaufman, L., Nell, J, Taylor, K., and Hayes, F. (1981). CALPHAD Comput. Coupling Phase Diagrams Thermochem. 5, 185. 

In order to construct the activity diagrams in a rigorous fashion, a certain amount of information must be available. Some experimental data for the mica-feldspar-kaolinite-gibbsite-montmorillonite relations are available. Data for the other minerals are often inferred from measurements of natural chemical parameters (K+, SiC, H+ concentrations in solutions) in situations where the different minerals are assumed to be stable. The relations between minerals can also be calculated as a function of K+, SiO and pH using thermochemical data for the participating phase (Hess, 1966) when they are known with precision. Frequently it is... 

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