NBS Tables

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 NBS Tables of Chemical Thermodynamic Properties," J. Phys. Chem. Ref. Data, ll(suppl. 2) (1982). 

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],... 

The standard enthalpies of formation of all the reactants and products of reaction 2.21 can be found in the NBS Tables of Chemical Thermodynamic Properties [17] Af77°(C2H5OH 60H2O, sin) = -287.72 kJ mol-1,... 

Why did we prefer to use the cycle in figure 2.1 instead of the easier method after equation 2.21 Simply because we had considered that the best data for the standard enthalpies of formation of pure ethanol and acetic acid are those recommended in Pedley s tables [15]. The values (-277.6 kJ mol-1 and -484.3 kJ mol-1, respectively) are both about 1 kJ mol-1 less negative than those in the NBS Tables, and their difference nearly cancels when the reaction enthalpy is calculated. But of course, we are seldom so lucky. Using data from different databases may lead to much larger discrepancies. 

Having thus settled on Pedley s tables for the pure organic compounds, we have then decided to use NBS Tables to derive the solution enthalpies in figure 2.1. The values can be easily evaluated from the differences between the standard enthalpies of formation of the compounds in solution and the standard enthalpies of formation of pure substances, viz. 

Reactive ionic compounds are therefore useless to derive hydration enthalpies (or more generally, solvation enthalpies). Fortunately, there are many alternatives. Take lithium chloride, for example, and data from the NBS Tables [ 17]. The enthalpy of solution of this solid in water, at infinite dilution, is given by... 

Extensive tables of standard heats of formation are available, but they are not all at the same reference temperature. The most convenient are the compilations known as the JANAF [1] and NBS Tables [2], both of which use 298 K as the reference temperature. Table 1.1 lists some values of the heat of formation taken from the JANAF Thermochemical Tables. Actual JANAF tables are reproduced in Appendix A. These tables, which represent only a small selection from the JANAF volume, were chosen as those commonly used in combustion and to aid in solving the problem sets throughout this book. Note that, although the developments throughout this book take the reference state as 298 K, the JANAF tables also list A// for all temperatures. 

Wagman DD, Evans WH, Parker VB, et al. 1982. The NBS tables of chemical thermodynamic properties. J Phys Chem Ref Data 11 1-293. 

D. D. Wagman, The NBS tables of chemical thermodynamic properties, J. Phys. Chem. Ref. Data 11, Supplement No. 2, (1982), pp. 2-7, pp. 2-14. Similar data can also be found listed by compound at http //webbook.nist.gov/chemistry/, the Chemistry WebBook of the National Institute of Science and Technology. 

D. D. Wagman, B. H. Evans, V. B. Parker et al.. The NBS Tables of Chemical and Thermodynamic Properties Selected Values for Inorganic and Ci and Ci Organic Substances in SI Units, American Chemical Society, New York, 1982. 

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