Thermodynamics of the systems NO –3= NO –2+½O2 and NO –3+½O 2–2= NO –2+ O –2 in molten alkali nitrates

Abstract

The thermodynamic parameters for the homogeneous phase reaction NO^–₃= NO^–₂+½O₂(a) in the (Na,K)NO₃ eutectic melt has been determined in the temperature range 500–700 K; ΔH_a= 114 kJ mol^–1 and ΔS⁰_a= 62 J mol^–1 K^–1. Appropriate catalysts have been used to favour the establishment of equilibrium conditions. The results are compared critically with all available data for reaction (a) in various nitrate solvents. On the basis of the van't Hoff equation and data we obtained previously for the “anhydrous” disproportionation of superoxide, the thermodynamic parameters for the reaction NO^–₃+½O^2–₂= NO^–₂+ O^–₂(b) have been calculated; ΔH_b= 95 kJ mol^–1 and ΔS⁰_b= 84 J mol^–1 K^–1.