The thermodynamics of diatomic condensation reactions: A simplified approach

Abstract

We have treated the thermodynamics of atom association reactions by realizing that in a formal sense, for a spherical model, the difference in the macroscopic free energy of vaporization and the bond dissociation free energy must equal the surface free energy. Our model makes two assumptions for the reaction C n−1+C→C n· 1. 1. The surface free energy term, ΔF 1, n−1 surf, is given by ΔF 1,n−1 surf=4πr c 2[n 2 3 γ n−(n−1) 2 3 γ n−1] where r c is the effective atomic radius computed from the macroscopic liquid density and the surface tension, λ n , is related to the macroscopic surface tension, λ ∞, by γ n=γ ∞ 1− 1 n 2. 2. The difference in the macroscopic entropy of vaporization and the bond dissociation entropy for n = 2 is negligibly small. The model works quite well for diatomic homonuclear and heteronuclear molecules.