Mathematical Methods for Computing Thermodynamic Functions from Spectroscopic Data

Abstract

Methods of summation are given for the Q-sum, and the related sums which are needed in calculating free energies, entropies and heat capacities from spectroscopic data. All necessary formulas are presented for the treatment of a linear molecule with arbitrary orbital angular momentum, spin multiplicity and nuclear symmetry. * Nineteen of the temperatures in this table are also used by Clayton and Giauque; comparison of the values of -(Fo-FoO) IT in the two tables shows exact agreement 14 times; the values of the present table are 0.001 lower four times, and 0.001 higher once.

Sulfur chemistry with time-varying oxygen abundance during Solar System formation

“…Lastly, we have included gaseous CrH from Burrows (private communication), gaseous FeH based on spectroscopic data in Dulick et al (2003), gaseous TiH from Bernath (private communication) and gaseous MgH based on spectroscopic data in Weck et al (2003). As no thermodynamic data were readily available for these four metal hydrides, the thermodynamic data are calculated from the dissociation potentials and partition functions, which are in turn calculated from asymptotic formulae for the vibrational and rotational constants of each electronic state (Kassel, 1933a(Kassel, , 1933b.…”

Heats, free energies, and equilibrium constants of some reactions involving O2, H2, H2O, C, CO, CO2, and CH4

“…N2 (gas).-Statistical calculations from Johnston and Davis [13], who gave values for the entropy, heat content, and h eat capacity to 5,000° K, and from Giauque and Clayton l15], who gave values for the free-energy function to 5,000° K. CO (gas).-Statistical calculations from Johnston and Davis [13], who gave values for the entropy, heat content, and heat capacity, to 5,000° K, and from Clayton and Giauque l16], who gave values for the free-energy function to 5,000° K. See also Gordon and Barnes [22], and Kassel [25] . CO2 (gas).-Statistical calculations from Kassel [19], who gave values for the free-energy function, heat content, and heat capacity, to 3,500° K. See also Gordon [26] and Gordon and Barnes [23].…”

Heat and free energy of formation of water and of carbon monoxide

“…These values for the change in heat content and entropy were then combined by means of the relation t:..F=t:..H-Tt:..S (1) to yield the value of t:..F0298. 16, which is the change in free energy associated with the given reaction at 25° 0, with each substance in the selected standard state.…”

“…16, which is the value of the change in heat content associated with the given reaction at 25° 0, with each reactant and product in the ideal state of unit fugacity (1 atmosphere).1 Then from the entropies of the various gases, which have been evaluated statistically by various investigators from spectroscopic and other molecular data, there was calculated the value of t:..s0298. 16, which is the change in entropy associated with the given reaction at 25° 0, with each reactant and product in the ideal state of unit fugacity. These values for the change in heat content and entropy were then combined by means of the relation t:..F=t:..H-Tt:..S (1) to yield the value of t:..F0298.…”