Energy. Heat of Formation. Thermodynamic Functions

8 Dissociation Energy. Heat of Formation. Thermodynamic Functions 

AfHo = AfH298.i5 = 339 10 kJ/mol being recommended in the 1971 JANAF Tables [2]. More recently, a spectroscopic value of Dg 3.60eV was derived from the Fourier transform IR emission spectrum of the v + 1 - v bands of NH(X with v = 0 to 4 the band centers were fitted to a polynomial expansion of G(v) up to fourth order of (v+1/2), and Dg was calculated by assuming that it corresponds to the v value ( 17) for which dG/dv = 0 [15]. 

Fitting a Rydberg-Klein-Rees-Vanderslice potential function for the ground state of NH (cf. p. 54) to the empirical Lippincott potential function (see [39]) resulted in Dq = 3.45 0.14eV [40]. 

The heat capacity C°, thermodynamic functions S°, - (G°-Hg9Q)/T, H -Hggg, and the equilibrium constant Kf for the formation of NH as an ideal gas from the elements have been calculated for a standard-state pressure of 1 atm and tabulated for 298.15 K and between 0 and 6000 K at 100 K intervals in the 2nd edition of the JANAF Tables [2 to 4] results of [2] are based on Dq(NH) = 3.6 eV, and the ground-state configuration 

Using the 1982 JANAF [4] thermodynamic and Huber-Herzberg [6] ground-state spectroscopic (including Dg) data, the dissociation function of NH between 1000 and 6000 K has been derived [52]. With the 1971 JANAF data [2], the coefficients of a power series approximation for the Gibbs free-energy function, -(G°-H29s)/T = cpo + 9 In x + (p 2 x + (p i x + (pi x + (p2 x + (p3 x where x = 10 T (T 6000 K), were calculated [53]. 

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