ABSOLUTE DETERMINATION OF THE TEMPERATURE BEHAVIOR OF THE NO2 + NO3 +(M) N2O5 + (M) EQUILIBRIUM

The temperature dependence of the NO2 + NO3 + (M) ↔ N2O5 + (M) equilibrium has been studied in the temperature range 279.6−294.2 K at a total pressure of 1000 mbar synthetic air in the 200 m3 EUPHORE simulation chamber facility in Valencia, Spain. Simultaneous determination of the concentration−time behaviors of NO3, NO2, and N2O5 were obtained using the DOAS technique for detection of the NO3 radical and FT-IR spectroscopy for detection of NO2, and N2O5. The experimental data are well described by ln([N2O5]/[NO2][NO3]) = −60.46 ± 0.26 + (10724 ± 75)/T where the errors given are random and expressed as 95% confidence limits. A critical comparison is made between the values of Keq determined in this work and those reported in the literature.