Thermochemical tables Thermodynamic

References D. D. Wagman, et ah, The NBS Tables of Chemical Thermodynamic Properties, in J. Phys. Chem. Ref. Data, 11 2,1982 M. W. Chase, et ah, JANAF Thermochemical Tables, 3rd ed., American Chemical Society and the American Institute of Physics, 1986 (supplements to JANAF appear in J. Phys. Chem. Ref. Data) Thermodynamic Research Center, TRC Thermodynamic Tables, Texas A M University, College Station, Texas I. Barin and O. Knacke, Thermochemical Properties of Inorganic Substances, Springer-Verlag, Berlin, 1973 J. B. Pedley, R. D. Naylor, and S. P. Kirby, Thermochemical Data of Organic Compounds, 2nd ed.. Chapman and Hall, London, 1986 V. Majer and V. Svoboda, Enthalpies of Vaporization of Organic Compounds, International Union of Pure and Applied Chemistry, Chemical Data Series No. 32, Blackwell, Oxford, 1985. 

D. D. Wagman and co-workers. The NBS Tables of Chemical Thermodynamic Properties Selected Valuesfor Inorganic and and C Organic Substances in SI Units, in /. Phys. Chem. Ref. Data, 11, suppl. 2 (1982) M. W. Chase, Jr. and co-sso-rkers, JMNAF Thermochemical Tables, 3rd ed.. Part II, in /. Phys. 

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. 

Heat Capacity, C° Heat capacity is defined as the amount of energy required to change the temperature of a unit mass or mole one degree typical units are J/kg-K or J/kmol-K. There are many sources of ideal gas heat capacities in the hterature e.g., Daubert et al.,"" Daubert and Danner,JANAF thermochemical tables,TRC thermodynamic tables,and Stull et al. If C" values are not in the preceding sources, there are several estimation techniques that require only the molecular structure. The methods of Thinh et al. and Benson et al. " are the most accurate but are also somewhat complicated to use. The equation of Harrison and Seaton " for C" between 300 and 1500 K is almost as accurate and easy to use ... 

Ideal gas absolute entropies of many compounds may be found in Daubert et al.,"" Daubert and Danner," JANAF Thermochemical Tables,TRC Thermodynamic Tables,and Stull et al. ° Otherwise, the estimation method of Benson et al. " is reasonably accurate, with average errors of 1-2 J/mol K. Elemental standard-state absolute entropies may be found in Cox et al." Values from this source for some common elements are listed in Table 2-389. ASjoqs may also be calculated from Eq. (2-52) if values for AHjoqs and AGJoqs are known. 

To make contact with atomic theories of the binding of interstitial hydrogen in silicon, and to extrapolate the solubility to lower temperatures, some thermodynamic analysis of these data is needed a convenient procedure is that of Johnson, etal. (1986). As we have seen in Section II. l,Eqs. (2) et seq., the equilibrium concentration of any interstitial species is determined by the concentration of possible sites for this species, the vibrational partition function for each occupied site, and the difference between the chemical potential p, of the hydrogen and the ground state energy E0 on this type of site. In equilibrium with external H2 gas, /x is accurately known from thermochemical tables for the latter. A convenient source is the... 

The choice of a given database as source of auxiliary values may not be straightforward, even for a thermochemist. Consistency is a very important criterion, but factors such as the publication year, the assignment of an uncertainty to each value, and even the scientific reputation of the authors or the origin of the database matter. For instance, it would not be sensible to use the old NBS Circular 500 [22] when the NBS Tables of Chemical Thermodynamic Properties [17], published in 1982, is available. If we need a value for the standard enthalpy of formation of an organic compound, such as ethanol, we will probably prefer Pedley s Thermodynamic Data and Structures of Organic Compounds [15], published in 1994, which reports the error bars. Finally, if we are looking for the standard enthalpy of formation of any particular substance, we should first check whether it is included in CODATA Key Values for Thermodynamics [16] or in the very recent Active Thermochemical Tables [23,24],... 

In the section on Thermochemistry in the International Critical Tables (see Bichowsky1), the values were recorded in joules, in the hope that thermochemists might come to use this fundamental unit in their calculations and writings. But the attempt to break away from the calorie as a unit in thermochemical and thermodynamical calculations proved to be unpopular and apparently hopeless of accomplishment. In order to satisfy the popular demand for the calorie as a unit in calculations and tabulations, and at the same time depart as little as possible from the fundamental unit of energy, the joule, in terms of which all accurate thermochemical measurements are actually made, we have used in this book a defined calorie, that is, one which has no actual relation whatever, except incidentally and historically, to the heat capacity of water. 

We will now consider a practical example of calculating thermochemical properties for the species CH3. Actually a lot is known about the CH3 radical, and we choose it as example in order to compare the calculated results with experimental data. The NIST-JANAF Thermochemical Tables [62] are a standard source for experimental thermochemical data, as well as moments of inertia, vibrational frequencies, and the like. The NIST-JANAF Tables use the same basic approach outlined here to calculate the temperature dependence for their thermodynamic data, based on species vibrational frequencies and moments of inertia. 

Fortunately, much experimental thermochemical information exists in the literature and in data compilations. The NIST-JANAF Thermochemical Tables [62] is a particularly useful source of data. In the following, we discuss some of the data conventions adopted by the NIST-JANAF Tables in reporting this information. These compilations adopt sound and useful conventions based on fundamental thermodynamic considerations. This brief discussion offers a simple explanation of the quantities reported there. 

For thermodynamic data, see N. Jacobson, Use of Tabulated Thermochemical Data for Pure Compounds, J. Chem. Ed. 2001, 78, 814 http //webbook.nist.gov/chemistry/ and http //www.crct.polymtl.ca/fact/ websites.htm M. W. Chase, Jr., NIST-JANAF Thermochemical Tables, 4th ed ... 

In the JANAF Thermochemical Tables [U.S. National Bureau Standards, NSRDS-NBS Pub. 37 (1971 and later)], thermodynamic data are tabulated at many different temperatures. 

Equation (41.12) is a key equation in thermodynamics, related to the van t Holf Equation (Frames 46 and 47) considered later, which can be used to interpret the thermodynamics of reactions (see Frame 47, section 47.2). Once rearranged to equation (41.16) it enables us to take AfG° data direct from thermochemical tables for example and calculate Kp of the reaction (41.1) under the standard conditions, (i.e. T = 298.15 K and P° = 1 bar). This can be done for reactions involving any chemical species for which standard data is available. Concentrations may well be employed in place of partial pressures. 

The thermochemical data for the product species are critical in the calculation of propellant performance. The methods of statistical thermodynamics have provided a reliable technique of establishing most of the thermochemical data required for propellant performance calculations. Again, the JANAF Thermochemical Tables (18) represent an extensive and widely used compilation of these data. 

The process of the calculation involves a reformer which gets its exergy not from combustion, but as electrical power generated by supplying CO and Fi2 to separate fuel cells which are able to create an excess above the need of the reformer. The invaluable JANAF thermochemical tables (Chase etah, 1985) provided the thermodynamic data. The excess is the chemical exergy of methane. 

JANAF Joint Army, Navy, Air Force Thermochemical Tables, 2nd ed., 1971. NSRDS-NBS 37, US Government Printing Office Washington, DC. See also later supplements for 1971-1981. Kohl, F. J., Stearns, C. A., and Fryburg, G. C. "Sodium Sulfate Vaporization Thermodynamics and Role in Corrosive Flames", 1975, NASA TMX-71641. 

Historically, the defined pressure for the standard state, i.e., the standard-state pressure, has been one standard atmosphere (101 325 Pa) and most existing data use this pressure. With the growing use of SI units, continued use of the atmosphere is inconvenient. lUPAC has recommended that the thermodynamic data should be reported for a defined standard-state pressure of 100 000 Pa. The standard-state pressure in general is symbolized as Previously in all JANAF thermochemical publications, was taken as 1 atm. In the current set of JANAF Thermochemical Tables p"" is taken as 100 000 Pa (1 bar). It should be understood that the present change in the standard-state pressure carries no implication for standard pressures used in other contexts, e.g., the convention that normal boiling points refer to a pressure of 101 325 Pa (1 atm). 

Our concern in the preparation of the JANAF Thermochemical Tables is to adjust any experimental measurements to the thermodynamic scale. In practice, this means converting to the IPTS-68 scale since it is the currently accepted closest approximation to the thermodynamic scale. 

In all previous JANAF Thermochemical Tables, the standard-state pressure was one atmosphere (101 325 Pa) and the unit of energy was the thermochemical calorie (4.184 J). For this publication, the standard-state pressure is changed to one bar (100 000 Pa) and the energy unit to the joule. The values from previous JANAF tabulations have been converted as described below. This information is provided not only to make clear the correspondence between this publication and previous JANAF Thermochemical Tables but also to assist the reader in making comparisons with other tables. This information is the same as that provided in The NBS Tables of Chemical Thermodynamic Proper-... 

Thermodynamic data for condensed states are derived from either measured or estimated information. The thermochemical table is obtained normally by the appropriate integration of heat capacity data. At the appropriate temperatures, transition enthalpies are added to the enthalpy total, while the quotient of the transition enthalpy divided by the thermodynamic temperature is added to the entropy total. 

L. V. Gurvich, I. V. Veits, et al., "Thermodynamic Properties of Individual Substances", Vol. 3, Nauka, Moscow, 1981. JANAF Thermochemical Tables (1983). 

J. D. Cox, chairman, CODATA Task Group on Key Values for Thermodynamics, J. Chem. Thermodynamics J, 903 (1978). JANAF Thermochemical Tables P (g), 12-30-82. 

The reverse rate constants for the elementary reactions used in the present work were caJculated from the forward rate constants and the equilibrium constant by assuming microscopic reversibility. Standard states used in tabulations of thermodynamic data are invariably at 1 atm and the temperature of the system. Since concentration units were required for rate constant calculations, a conversion between Kp and Kc was necessary. Values of Kp were taken from the JANAF Thermochemical tables (1984). Kc was calculated from the expression ... 

Hamblin, F.D., Abridged Thermodynamic and Thermochemical Tables (S.I. Units ), Pergamon Press, Elmsford, N.Y. (paperback edition available), 1972. 

Thermodynamic properties of the Si3N4 compound were also reassessed based on the JANAF thermochemical tables [61]. 

The thermodynamic parameters for Reaction (8.2) in the gas phase, as calculated from the JANAF Thermochemical Tables [359aa], are detailed in Table 8.1, and illustrated in Figures 8.3 and 8.4 [1825a]. Further details of this dissociation reaction are given in Sections 5.1.2 and 6.1.4. 

Selenium forms compounds with most elements of the Periodic Table. NEA-TDB selected data for a number of these elements are not available for use as auxiliary data in the evaluation of formation data and entropies of their selenium compounds from reaction data. It would not have been a realistic task for the selenium project to assess all non-selected auxiliary data needed according to the NEA-TDB Guidelines. Instead the information required was obtained from compilations of thermochemical data such as The NBS tables of chemical thermodynamic properties and JANAF thermochemical tables supplemented by Critical reviews of. .. published in chemical Journals. The review of the literature on selenium and its compounds has thus resulted in two thermochemical data sets. One set of data is in accord with the NEA-TDB Guidelines and compatible with the requirements for addition to the NEA-TDB Data Bank. The other set, obtained with non-TDB auxiliary data, does not fulfil the requirements of the Data Bank. These facts created a problem in the presentation of the results of the selenium project, which was solved by the... 

Rossini, F. D. Selected values of physical and thermodynamic properties of hydrocarbons and related compounds. Pitsburgh Carnegie Press 1953 JANAF thermochemical tables, Stull, D. R. (project director). Midland, Michigan Dow Chemical Company 1965... 

A reliable source for thermodynamic data is JANAF Thermochemical Tables. 3d ed.. which lists the thermodynamic data of over 1800 substances. 

One of the more comprehensive and reliable sources of thermodynamic data is the JANAF thermochemical tables. 

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