Thermodynamic data

Thermodynamic data will be used to calculate AH as a function of temperature between 298 and 1000 K. AG and K will then be calculated over the same temperature range. Finally, the equilibrium composition of a stoichiometric mixture of carbon monoxide and hydrogen at a temperature of 600 K and a pressure of 300 atm will be obtained. 

The information in Table 2 was obtained from ref. 5. Table 3 gives the heat capacities of the three reactants taken from ref. 9. 

The factor 1 calorie = 4.184 J has been used where necessary to convert values published in calories to joules. 

Standard enthalpies of formation, entropies and Gibbs free energies of formation [5] 

TABLE 3 Heat capacities Cp/Jmor K as power series in - a + b T/K) + T [9] c TIKf + d(TIKf  

Thermodynamic Data.—While ultimately one hopes to understand adsorption phenomena in terms of molecular concepts, it is nevertheless of considerable interest to examine the behaviour of purely thermodynamic quantities as a function of experimental variables such as temperature and composition. Indeed analysis of data in this way is likely to indicate the direction in which theoretical treatments have to be developed. 

As stressed by Vernov and Lopatkin it is important that the quantities concerned must be derivable from experimental data without the intervention of a molecular model. Convenient functions satisfying this criterion are (i) the difference (cr —orf), between the interfacial tension cr between liquid mixture and the solid and o-f, that between pure component 2 and the solid (ii) the difference between the areal enthalpy of immersion of the solid in the liquid mixture, and in the pure liquid 2, (iii) the corresponding difference 

Strictly speaking this procedure involves the use of a theoretical model for the calculation of the surface area of the solid from, for example, gas adsorption data. This objection can be overcome, as advocated by Schay, by working in specific quantities. But it then becomes difiicult to intercompare results obtained on different samples of solid. 

The use of equation (1) integrated across the whole composition range to obtain ( rf — of) to check the thermodynamic consistency of measurements on binary systems formed from components 1,2, and 3 is becoming an accepted procedure. Analysis of data to obtain (of —o) as a function of X2 is less common. 

Thomas and Eon have analysed their data on the systems (acetone+ carbon tetrachloride), (acetone+benzene), and (benzene+carbon 

The thermodynamic data for the substances employed in lead-acid batteries are compiled in Table 4. 

Substance Enthalpy of formation HO.s (kJmol ) Free enthalpy of formation G (kJ mof ) Entropy, S-ts (JK mol ) 

The active material comprises the substances that constitute the charge-discharge reaction. In the positive electrode of lead-acid batteries, the active material in the charged state is lead dioxide (PbOj), which is converted into lead sulfate (PbS04) when the electrode is discharged. The active material is the most essential part of a battery, and battery technology has to aim at optimum constitution and performance for the expected application. This does not only concern the chemical composition but also the physical structure and its stability. Specialized methods have been developed to fulfill these requirements, and the primary products as well as the manufacturing process are usually specified by the individual battery manufacturer. 

It is characteristic for battery manufacture is that lead dioxide (Pb02) as the charged state of the active material is al- 

The charge-discharge reactions occur at the phase boundary between the active material and the electrolyte. To make sure that a sufficient rate of reaction is achieved, the surface of the reacting materials has to be large. Otherwise, the kinetic parameters would reduce the reaction rate too much. Table 5 shows the surface areas of the active materials in the positive and the negative electrode. 

Substance Enthalpy of formation, (k mol- ) Free enthalpy of formation, (k) mol- ) Entropy, (1 K- mol- ) 

Pb02 as Active Material in Lead-Acid Batteries 

It is characteristic for battery manufacture that lead dioxide (Pb02) as the charged state of the active material is always generated by electrochemical oxidation. Thus, electron-conducting bridges are established between the fine particles, and a matrix is formed of comparatively low electronic resistance. Three general types of positive electrodes are mainly used today Plante, pasted, and tubular plates, which vary not only in their design but also in the way they are manufactured. 

This category was used to provide chemical and physical data for nitric acid. The references also contain extensive details of chemical equilibria appropriate to the process, and several formulae used in the mass and energy balance calculations. 

Reference TDI contains an enthalpy table for ammonia at different pressures. Reference TD2 contains a series of tables in an appendix from which the specific heats of the reaction-gas mixture were calculated. Humidity charts were also useful. Reference TD3 is valuable for its steam tables, while Ref. TD4 contains both thermodynamic and chemical equilibria data for nitric acid. The final reference, Robertson and Crowe (Ref. TD5), contains formulae and tables for the sizing and choice of an air-feed compressor. 

It seems more appropriate to include the Bibliography after the Literature Survey rather than at the end of the report. 

Kirk and D.F. Othmer (Eds), Encyclopedia of Chemical Technology, 3rd Edn, Volume 15, pp.853-871, Wiley-lnterscience, New York (1981). 

Lowenheim and M.K. Moran (Eds), Faith, Keyes and Clark s Industrial Chemicals, 4th Edn, pp.563-570, Wiley-lnterscience, New York, (1975). 

The CALPHAD method of computer coupling of phase diagrams and thermodynamics [24] was used to explore the phase equilibria in the Si-B-C-N system. Analytical descriptions of the Gibbs free energies for all stable phases and gaseous species of the system were established in the literature and by the 

Phase Pearson symbol Space group Proto-type Lattice parameters, nm a b c Comment 

The thermodynamic descriptions are based on data for the pure elements Si, B, C and N, respectively, as provided by Dinsdale [31] and stored in the SGTE database [32]. The gas phase consists of numerous gas species. The most important are listed in Table 2. 

The ternary system Si-B-C was optimized in the scope of our work on the Si-B-C-N system [33, 34]. The other three ternary systems (Si-B-N, Si-C-N, B-C-N) could be calculated comprehensively by thermodynamic extrapolations since all solid phases have negligible ranges of solubility. Thermodynamic data of the ternary phases pSiCJti4 and Si2CN4, are not known yet, however they are reported not to be stable at the conditions treated here (P = 1 bar, T 1300 K) [21]. 

The descriptions of all ternary systems were combined in one dataset to simulate the phase equilibria in the quaternary Si-B-C-N system. The results of the thermodynamic calculations of individual systems are shown in the corresponding sections. Thermodynamic models used are the Redlich-Kister polynomial [39], extrapolations according to Muggianu et al. [40] and the compound energy formalism [41] to describe the solid solution phases )S-boron, SiBn, SiBg, SiBs and B4+ C. 

The reduction of dioxygen to water may occur via a number of intermediate states having various thermodynamic stabilities. These are compounds with hydrogen and their different ionized (deprotonated) forms. The standard redox potentials relevant to reduction to hydrogen peroxide and subsequently to water are listed in Table II [20,21]. 

1 atm fugacity. It is often convenient to have redox potentials for aqueous solutions with 0 (aq) as the standard state for dioxygen. This 

Standard potentials for the reduction of dioxygen to water via hydrogen peroxide (25 °C, 1 atm 0 fugacity) 

Reduction potentials (V) for dioxygen species in aqueous solutions with O Caq) as standard state 

The stabilities of some H-0 and 0-0 bonds in terms of bond dissociation energies are listed in Table IV). 

Any reaction has associated with it changes in enthalpy (AH), entropy (A5), and free energy (AG). The principles of thermodynamics assure us ftiat AH, AS, and AG are 

Extensive discussions of techniques for studying reaction mechanisms are presented in E. S. Lewis, ed., Investigation of Rates and Mechanism of Reactions, Techniques of Chemistry, 3rd ed., Vol. VI, Part I, John Wiley Sons, New York, 1974 C. F. Bemasconi, ed.. Investigation of Rates and Mechanism of Reactions, Techniques of Chemistry, 4th ed., Vol. VI, Part I, John Wiley Sons, New York, 1986. 

CHAPTER 4 STUDY AND DESCRIPTION OF ORGANIC REACTION MECHANISMS 

Furthermore, the value of AG is related to the equilibrium constant K for the reaction 

Because these various quantities are characteristics of the reactants and products but are independent of the reaction path, they cannot provide insight into mechanisms. Information about AG, AH, and AS does, however, indicate the feasibility of any specific reaction. The enthalpy change of a given reaction can be estimated from tabulated thermochemical data or from bond-energy data such as those in Table 1.3 (p. 14) The example below illustrates the use of bond-energy data for estimating the enthalpy of a reaction. 

and AG are independent of the reaction path. They are interrelated by the fundamental equation 

1 Various sources The NBS Tables of Chemical Thermodynamic Properties (1982), J. Phys. Chem. Ref. Data, 11 (Supplement No. 2) TRC Thermodynamics Tables—Hydrocarbons. College Station, TX Thermodynamics Research Center. 

Various sources including the TRC Thermodynamic Tables—Hydrocarbons. College Station, TX Thermodynamics Research Center. 

The thermodynamic study of thiazole and of some of its binary mixtures with various solvents has led to the determination of important practical data, but also to the discovery of association phenomena between thiazole and some solvents and of thiazole self-association. 

The first binary mixture quantitatively studied was the water-thiazole system, thiazole being a very hygroscopic compound (104), Determining the purity of thiazole sample obtained by distillation, Metzger and Distel-dorf (287) observed the existence of a stable azeotropic mixture, the characteristics of which are the following  

The vapor-liquid equilibrium of the binary mixture is well fitted by Van Laar s equations (228). It was determined from 100 to 760 mm Hg. and the experimental data was correlated by the Antoine equation (289, 290), with P in mm Hg and t in °C  

The normal boiling point of pure thiazole is 118.241 0.004°C. 2-Methylthiazole behaves similarly, fitting the Antoine equation (291)  

The normal boiling point of 2-methylthiazole is 17 0= 128.488 0.005°C. The purity of various thiazoles was determined cryometrically by Handley et al. (292), who measured the precise melting point of thiazole and its monomethyl derivatives. Meyer et al. (293, 294) extended this study and, from the experimental diagrams of crystallization (temperature/degree of crystallization), obtained the true temperatures of crystallization and molar enthalpies of fusion of ideally pure thiazoles (Table 1-43). 

The data sets WATEQ4F.dat, MINTEQ.dat, PHREEQC.dat and LLNL.dat are automatically installed with the program PHREEQC and can be chosen from the menu item Calculations/File under Database File. The internal structure of these thermodynamic data sets has already been explained in great detail in chapter 

Lines beginning with are only commends, e.g. each first line of the species defined in the block SOLUTIONSPECIES. 

If elements, species, stability constants, and/or solubility constants that are unavailable in an existing data set, should be used for one task only, it is advisable to define them directly in the input file rather than to change the data set itself. As a declaration in an input file always has a higher rank, it overwrites information of a data set. Like in a data set, the keyword SOLUTION MASTER SPECIES has to be used to define the element (e.g. C), the ionic form (e.g. C03-2), the contribution of the element to alkalinity (e.g. 2.0), the mole mass of the species for 

Soon after the first isolation of milligram amounts of technetium, thermodynamic properties of the element and of several technetium compounds were determined [8]. Currently known thermodynamic data on enthalpies AH°, entropies. S . and Gibbs free energies AG°f are compiled in Table 6.3.A. 

Technetium metal melts at 2413 20 K [45]. The melting point is near those of other elements in the same period of the periodic system, e.g., molybdenum (2893 K) or ruthenium (2723 K). Rhenium melts more than 1000° higher (3453 K) than technetium, while the melting point of manganese (1.533 K) is considerably lower. The heat of melting of technetium was estimated to be 5.5 kcal molc [37], the entropy of fusion df5 to be 3.3 cal mole [38], the heat of sublimation at 298.15 K as 152  

2 kcal mole [47], the normal boiling point at 4900 K and the accompanying heat of vaporization is 138 kcal mole [37]. The heal capacity of technetium metal increases slightly from 6.87 cal-mole -K at 1000 K to 7..34 cal mole K at 1600 K [46], the liquid heat capacity was calculated as 11.2 cal - mole K [38], and the heat capacity for monoatomic technetium vapor as 4.98 cal mole K at 298 K [37], 

The melting point of 10207 was determined to be 392.6 0.1 K [50]. Extrapolation of the vapor pressure of liquid TC2O7 yielded a boiling point of 584 2 K [51]. The vapor pressure of crystalline and liquid TC2O7 follows a two-term equation between 298 and 533 K [51]  

Tuble 6.3.A Thermodynamic data of elemental technetium and some of its compounds at 298.15 K. 

Note Operations involving the tensor r eire given for symmetrical t only. 

Data from R. B. Bird, W. E. Stewart, and E. N. Lightfoot, Transport Phenomena, p. 738. Wiley, New York, 1960. 

Urey s calculations (1956) also are based on several arbitrary assumptions it is postulated that the carbon in the Earth s crust was 

The idea that free carbon might already have existed on the Earth s surface before the generation of life and the appearance of photosynthetic oxygen, in the form of the dynamically stable phase—graphite—seems more sound. In that case gaseous equilibrium in the atmosphere was controlled by a graphite buffer (Mel nik, 1972a). 

A calculation based on the presumed buffer reaction in which graphite participates  

The partial pressures of CH4 and H2O, like the overall fluid pressure (Pf), depend on the fugacity of hydrogen arriving from deep sources under a certain pressure. The quantitative relationships between these gases are determined by the reactions  

The calculated composition of a fluid in equilibrium with the association fayalite + metallic iron + graphite at different Pf and P is given in Fig. 20 (the relative amounts of the gases are shown in molar percentages). It is typical that the atomic ratio H/C = 5 hardly varies in a wide pressure range (from 15 to 2-3 kbar). At these pressures the (H + C)/0 ratio Ukewise varies little. Only when the pressure decreases to 0.5-1.5 kbar do both these ratios 

Bipyridyl, terpyridyl, and phenanthroline behave as weak bases, usually forming monoprotonated species. Typical values for the first 

Charton 152) has successfully applied the extended Hammett equation to these data and discussed the macroconstant, pA , in terms of the tautomerism 

Reproduced from 15Z) and (239) by the kind permission of the American Chemical Society. 

Diverse pieces of evidence suggest that a change in protonation site is unlikely. 

Fahsel and Banks (239) reasonably propose similar structures, e.g., (5), to that in (4) to account for such species as [H(phen)s]+, thus implying the participation of HgO for all the protonated phenanthroline molecules. 

A critical objective of any bonding theory is to explain the energies of chemical compounds. Inorganic chemists frequently use stability constants, sometimes called formation constants, as indicators of bonding strength. These are equilibrium constants for reactions that form coordination complexes. Here are two examples of the formation of coordination complexes and their stability constant expressions  

Data from R. M. Smith and A. E. Martell, Critical Stability Constants, VoL 4, Inorganic Complexes, Plenum EVess, New York, 1976, pp. 40-42,96-119. Not all ionic strengths were identical for these detmninations, but the trends in K values shown here are consistent widi determinations at a variety of ionic strengths. 

Enthalpies of reaction can be measured by calorimetric techniques. Alternatively, the temperature dependence of equilibrium constants can be used to determine A/f° and A5° for these ligand substitution reactions by plotting In K versus /T. 

Thermodynamic parameters such as A//°, A5 , and the dependence of K with T are useful for comparing reactions of different metal ions reacting with the same ligand or a series of different ligands reacting with the same metal ion. When these data are available for a set of related reactions, correlations between these thermodynamic parameters and the electronic structure of the complexes can sometimes be postulated. However, exclusive knowledge of the A//° and A.S° for a formation reaction is rarely sufficient to predict important characteristics of coordination complexes such as their structures or formulas. 

The complexation of Cd with methylamine and ethylenediamine are compared in Table 10.2 for  

DESCRipnoN OF Any reaction will have associated with it a change in enthalpy (A//), entropy 

Example 4.1, Calculate the enthalpy change associated with hydrogenation of butene. 

Estimated values for the standard enthalpies of formation AH298 kcal/mol and entropies 

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The calculation of vapor and liquid fugacities in multi-component systems has been implemented by a set of computer programs in the form of FORTRAN IV subroutines. These are applicable to systems of up to twenty components, and operate on a thermodynamic data base including parameters for 92 compounds. The set includes subroutines for evaluation of vapor-phase fugacity... 

American Petroleum Institute, Bibliographies on Hydrocarbons, Vols. 1-4, "Vapor-Liquid Equilibrium Data for Hydrocarbon Systems" (1963), "Vapor Pressure Data for Hydrocarbons" (1964), "Volumetric and Thermodynamic Data for Pure Hydrocarbons and Their Mixtures" (1964), "Vapor-Liquid Equilibrium Data for Hydrocarbon-Nonhydrocarbon Gas Systems" (1964), API, Division of Refining, Washington. 

Maczynski, A. "Thermodynamic Data for Technology—Verified Vapor-Liquid Equilibrium Data," Panstwowe Wydawnictwo Naukawa, Warsaw, Volume 1, 1976 Volume 2, 1978. 

For pure organic materials, it is also possible to calculate the heating value starting from the heats of formation found in tables of thermodynamic data. The NHV is obtained using the general relation of thermochemistry applicable to standard conditions of pressure and temperature (1 bar and 25°C)) f 9j... 

Example of NHV calculation for toluene based on thermodynamic data from Thermodynamic Tables - Hydrocarbons" edited by TRC (Thermodynamic Research Center, The Texas A M University System College Station, Texas, USA). 

Keller J B and Zumino B 1959 Determination of intermolecular potentials from thermodynamic data and the law of corresponding states J. Chem. Phys. 30 1351... 

Assuming that an equilibrium is now well established, the simulation may be restarted (not newly started) to begin with the sampling of structural and thermodynamic data. In our model case, data acquisition was performed for 3 ns (trajectory data plot not shown). For the production phase, also, the time evolution of the variables mentioned above should be monitored to detect stability problems or con-... 

Molecular dynamics simulations provide information about the motion of molecules, which facilitates the interpretation of experimental results and allows the statistically meaningful sampling of (thermodynamic) data. 

Chemists are interested not only in the thermodynamics of a process (the relative stability o the various species) but also in its kinetics (the rate of conversion from one structure tc another). Knowledge of the minimum points on an energy surface enables thermodynamic data to be interpreted, but for the kinetics it is necessary to investigate the nature of the... 

Resonance stabilization energies are generally assessed from thermodynamic data. If we define to be the resonance stabilization energy of species i, then the heat of formation of that species will be less by an amount ej than for an otherwise equivalent molecule without resonance. Likewise, the AH for a reaction which is influenced by resonance effects is less by an amount Ae (A is the usual difference products minus reactants) than the AH for a reaction which is otherwise identical except for resonance effects ... 

The composition to the melting point is estimated to be 65% Na AlF, 14% NaF, and 21% NaAlF [1382-15-3], The ions Na" and F ate the principal current carrying species in molten cryoHte whereas the AIF is less mobile. The stmctural evidences are provided by electrical conductivity, density, thermodynamic data, cryoscopic behavior, and the presence of NaAlF in the equiUbtium vapor (19,20). 

Ethyleneimine (El) and its two most important derivatives, 2-methyla2iridine [75-55-8] (propyleneimine) (PI) and l-(2-hydroxyethyl)a2iridine [1072-52-2] (HEA) are colodess Hquids. They are miscible ia all proportions with water and the majority of organic solvents. Ethyleneimine is not miscible with concentrated aqueous NaOH solutions (>17% by weight) (24). Ethyleneimine has an odor similar to ammonia and is detectable only at concentrations >2 ppm. The physical properties of ethyleneimine and the derivatives mentioned are given ia Table 1. Thermodynamic data can be found ia the Hterature (32). 

TRCTHERMO Thermodynamic Research Center, Texas A M University, College Station, Texas thermodynamic data... 

Thermodynamic data (4) for selected manganese compounds is given ia Table 3 standard electrode potentials are given ia Table 4. A pH—potential diagram for aqueous manganese compounds at 25°C is shown ia Figure 1 (9). 

Table 3. Thermodynamic Data for Crystalline Aluminum Hydroxides at 298.15K and 0.1 MPa ...

Thermodynamic data are available only for the lower alkylamines, mainly estimates based on a few experimental deterrninations (3,4). Many manufacturing processes appear to be limited by thermodynamic equiUbria. The lack of accurate free energy data for these amines limits the appHcation of thermodynamic considerations, in contrast to the situation in hydrocarbon technology. 

K. C. Mils, Thermodynamic Data forinorganic Sulphides, Selenides, andTellurides, Butterworths, Ltd., London. 

The thermodynamic properties of sulfur trioxide, and of the oxidation reaction of sulfur dioxide are summarized in Tables 3 and 4, respectively. Thermodynamic data from Reference 49 are beheved to be more accurate than those of Reference 48 at temperatures below about 435°C. 

The exothermic oxidation reaction is carried out ia the gas phase at temperatures of 1200°C or higher. Relevant thermodynamic data are given ia Table 11. ... 

The most important haUdes and oxyhaUdes are shown in Table 16. General introductions to the chemistry of the titanium haUdes are available (10,120). Thermodynamic data are given in Tables 1 and 2. 

B. D. Smith and R. Srivastava, Thermodynamic Data for Pure Compounds Part A.. Hydrocarbons and Ketones, Elsevier, Amsterdam, the Netherlands, 1986. T. Boubhk, V. Eried, and E. Hala, The Hapour Pressures of Pure Substances, 2nd ed., Elsevier, Amsterdam, the Netherlands, 1984. 

The physical properties of bismuth, summarized ia Table 1, are characterized by a low melting poiat, a high density, and expansion on solidification. Thermochemical and thermodynamic data are summarized ia Table 2. The soHd metal floats on the Hquid metal as ice floating on water. GaUium and antimony are the only other metals that expand on solidification. Bismuth is the most diamagnetic of the metals, and it is a poor electrical conductor. The thermal conductivity of bismuth is lower than that of any other metal except mercury. 

Table 2. Thermodynamic Data for Carbon Monoxide (Ideal Gas) b ...

Chromatographic separations rely on fundamental differences in the affinity of the components of a mixture for the phases of a chromatographic system. Thus chromatographic parameters contain information on the fundamental quantities describing these interactions and these parameters may be used to deduce stabiUty constants, vapor pressures, and other thermodynamic data appropriate to the processes occurring in the chromatograph. 

Flame Temperature. The adiabatic flame temperature, or theoretical flame temperature, is the maximum temperature attained by the products when the reaction goes to completion and the heat fiberated during the reaction is used to raise the temperature of the products. Flame temperatures, as a function of the equivalence ratio, are usually calculated from thermodynamic data when a fuel is burned adiabaticaHy with air. To calculate the adiabatic flame temperature (AFT) without dissociation, for lean to stoichiometric mixtures, complete combustion is assumed. This implies that the products of combustion contain only carbon dioxide, water, nitrogen, oxygen, and sulfur dioxide. 

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