A kinetic study of the decomposition of HNO 3 and its reaction with NO

The rate of reaction between NO and HNO 3 and the rate of thermal decomposition of HNO 3 have been measured by FTIR spectroscopy. The measurements were made in a teflon lined batch reactor having a surface to volume ratio of 14 m −1 . During the experiments, with initial HNO 3 concentrations between 2 and 12 ppm and NO concentrations between 2 and 30 ppm, a reactant stoichiometry of unity and a first order NO and HNO 3 dependence were confirmed. The observed rate constant for the reaction\documentclass{article}\pagestyle{empty}\begin{document}$${\rm HNO}_{\rm 3} + {\rm NO} \longrightarrow {\rm HNO}_{\rm 2} + {\rm NO}_2$$\end{document} at 22°C and atmospheric pressure was determined to 1.1 (±0.3) 10 −5 ppm −1 min −1 . At atmospheric pressure, HNO 3 decomposes into NO 2 and other products with a first order HNO 3 dependence and with a rate constant of 2.0 (±0.2) 10 −3 min −1 . The apparent activation energy for the decomposition is 13 (±4) kJ mol −1 .