A spectroscopic study of the nitrogen dioxide-dinitrogen tetroxide system by the infrared absorption technique

Abstract

Publication costs assisted by the US. Environmental Protection AgencyWe report the results of a new technique for the determination of the equilibrium constant for the reactions N204 + 2N02. Fourier transform spectroscopy was used to record infrared spectra of the u2 band of NO2 near 13.3 I*. Spectra were recorded alternately through two absorption cells of different lengths. Working within the validity of the Beer-Lambert law of absorption of radiation, an equation is derived which relates the equilibrium constant to pairs of gas pressures which give the same spectral absorbance of NO2 in the two unequal cells. No knowledge of the absorption coefficient is needed using this technique. All samples were pressurized to 740 Torr with high-purity nitrogen and measurements were taken a t room temperature (296 f 1 K). Using this two cell technique, we have found K,, = 0.14 f 0.02 atm at room temperature.

Room-temperature rate constant for the hydroperoxo + hydroperoxo reaction at low pressures

“…44 Similarly, N02 dimerization in the flow tube is negligible for [N02] ~1 X 1013 molecules cm'3 at 298 K since Kf = FNo22/Pn2o4 = 106 torr. 45 After completion of the H02 to N02 conversion experiments, the microwave discharge that produced the Cl atoms was turned off. No N02 was produced by reactions between the gases, for the Cl + CH3OH + 02 and Cl + H202 sources, when the discharge was off.…”

Rate constant for formation of chlorine nitrate by the reaction ClO + NO2 + M

“…At pressures above 9 Torr the logarithmic CIO decay was nonlinear, with downward curvature. This effect was attributed to poor radial mixing, and the data were not considered suitable for calculation of rate constants.…”

Nitrogen dioxide reactions with atomic lanthanide cations and their monoxides: gas-phase kinetics at room temperature

“…In contrast with the vast majority of gaseous reagents that have been studied previously in our laboratory NO 2 has a high propensity toward dimerization, leading to the formation of the N 2 O 4 molecule. The equilibrium constant for the dimerization reaction of NO 2 (Reaction 1) has a value of K = 7.00 (eqn (2a), standard state, P 0 = 1 atm) at 298 K. 56 Using eqn (2b), and a value of DH rxn = À13.65 kcal mol À1 for the forward reaction, 57 we can derive a value of K = 8.85 for the equilibrium constant at 295 K.…”