Thermodynamic properties of the alkali metals
William H. Evans, Rosemary Jacobson, Thomas R. Munson, Donald D. Wagman
1955
Journal of research of the National Bureau of Standards
The a va ilable data on the thermodynamic properties of the elem ents lithium, sodium, p otassi um, rubidium, a nd cesium have been analyzed, a nd selected values of these properties are presented in tabular form . The tables inclu de valu es of the free-energy function, (F°-HO)/ T ; heat-content function, (H O-H a) / T; entropy, S o; heat content, (l-I°-H a) ; heat capacity, C~; heat of formation, !!.l--Ij" ; free energy of format ion, !!.Fj"; and logarithm of tlle equilibrium constant of
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... tion, log Kf , for the solid, the liquid, and the monatomic a nd diatomic gases as a function of temperature from 0° K to high temperatures. 1 P resen t address: Department of Chemist ry, Uni versity of Michigan , An n Arhor, Mich . , Present address: The Vitro Corporation, West Orange, N . J. 3 Figures in b rackets indicate the literature references at t he end of this paper. 83 3 . Calculation of the Thermodynamic Functions 3.1. Monatomic Gases The translational contributions to the thermodynamic fun ctions of the monatomic gases Li, N a, K , Rb , and Os were calculated by use of t be equaLions given by Wagman et al. [6] (corrected for t he new defini tion of the thermochemical caloric). The additional contributions due to electronic excitation are easily obLained in terms of t he par tition function , Q, a nd tbe derived fun ctions Q' a nd Q" Q' = ~i gi (~dkT) e-E .lk T These conlributions were evalu ated by direct summation. Th e energy levels, Ei , and multiplicities, gi , were taken from Moore [9] . The factor hcJk, used to convert wave numbers to degree, was taken as 1.43847. From these, the electronic contributions to the t bermody namic functions arc easily obtained -(F°-H~) / T= mnQ (HO-H~) / T= R ( Q' / Q ) CO= R[Q" / Q_ (Q' / Q) 2]. Diatomic Gases The translational contributions to th e thermodynamic functions for the diatomic molecules Liz, N az, K 2, Rb2, and CS2 wer e evaluated with t he sam e equations used for the mona tomic gases. The ro tational and vibrational constants given in table 1 were used to calculate the thermodynamic functions for a rigid rotator [6] with moment of inertia, I , equal to h/ [87r2CBe(1-ae/2 )], and symmetry number 2, and for an independent harmonic oscillator [1 0] with a fundamental frequency of (w e-2xewe) .4 , The spectroscopic notation is that used by H er zb erg [12] .
doi:10.6028/jres.055.010
fatcat:d3odwpy7cffudpkdfhxm64diwy