A spectroscopic study of the equilibrium NO₂ + NO₃ + M 2 N₂O₅ + M and the kinetics of the O₃/N₂O₅/NO₃/NO₂/ air system

Abstract

The equilibrium constant, K,, of the reaction NO2 + NO3 + M N z O~ + M has been determined for a small range of temperatures around room temperature in air at 740 torr by direct spectroscopical measurements of NOz, NOS, and NzOs. At 298 K, K, was determined as (3.73 2 0.61) x lo-'' cm3 molecule-'. Averaging this and 11 other independent evaluations of K, yields K. , = (3.31 f 0.82) x lo-" cm3 molecule-', where the uncertainty is given as one standard deviation. The kinetics of the 03/NOz/Nz05/N03/air system was studied in a static chamber at room temperature and 740 torr total pressure. Evidence of a unimolecular decay reaction of NO3, NO3 + NO + Oz, was found and its rate coefficient was estimated as (1.6 2 0.7) x s-' at 295 2 2 K.

Temperature dependence of the NO3 absorption cross-section above 298 K and determination of the equilibrium constant for NO3 + NO2↔ N2O5 at atmospherically relevant conditions

“…9. The results presented here are larger than those by Wa¨ngberg et al 6 (up to a factor of B1.5 at 298 K) and Burrows et al, 25 and agree with that of Hjorth et al 26 and the most recent study by Cantrell et al, 5 who calculated the equilibrium constant from the thermal decomposition rate coefficient of N 2 O 5 (k À1 ) and literature values of the forward rate coefficient (k 1 ). Most studies, with the exception of the data by Burrows et al, 25 exhibit a temperature dependence of the equilibrium constant that is very similar to our work.…”

Preparation and accurate measurement of pure ozone

“…36,37 In the presence of residual layers of water molecules, HNO 3 is a likely reaction product, but HNO 2 may also be produced. In principle, HNO 3 is also formed via the slow hydrolysis reaction of N 2 O 5 that occurs in gas phase, but this reaction can be ignored here due to its extremely slow rate.…”

Heterogeneous atmospheric degradation of current-use pesticides by nitrate radicals

“…where S 1 is the silica particle surface (m 2 g -1 ). Graham et al, 1974 NO 3 + isoprene → Products (6.5 ± 0.2) × 10 -13 Atkinson et al, 1984 O 3 + isoprene → Products (9.6 ± 0.7) × 10 -18 NO 2 + isoprene → Products (10.3 ± 0.3) × 10 -20 NO 3 + O 3  Products 1•10 -17 Hjorth et al, 1992 NO 3 + NO 2  O 2 + NO + NO 2 6.56•10 -16 DeMore, 1997…”