Study of the reactions of OH with HCl, HBr, and HI between 298 K and 460 K

Abstract

The reactions between OH radicals and hydrogen halides (HCl, HBr, HI) have been studied between 298 and 460 K by using a discharge flow-electron paramagnetic resonance technique. The rate constants were found to be k HCl (298 K) = (7.9 ± 1.3) × 10 −13 cm 3 molecule −1 s −1 with a weak positive temperature dependence, k HBr (298-460 K) = (1.04 ± 0.2) × 10 −11 cm 3 molecule −1 s −1 , and k HI (298 K) = (3.0 ± 0.3) × 10 −11 cm 3 molecule −1 s −1 , respectively. The homogeneous nature of these reactions has been experimentally tested.

Rate Constant of the Reaction of OH Radicals with HBr over the Temperature Range 235–960 K

“…Figure summarizes the results of the present measurements of k 1 in comparison with those from three previous temperature dependence studies realized in overlapping temperature ranges. ,, Concerning the results from this study, one can note an excellent agreement between absolute and relative measurements of the reaction rate constant. In the range of the reported uncertainties on the measurements of k 1 , the current data ( T = 235–960 K) match very well with those from previous study from this group ( T = 230–360 K), as well as the laser flash photolysis-resonance fluorescence measurements of Ravishankara et al ( T = 249–416 K) and recently reported results of discharge flow electron paramagnetic resonance study by Khamaganov et al ( T = 298, 370, and 460 K) . Three most recent room temperature measurements of the reaction rate constant (reporting the values of k 1 between 0.92 and 1.12 × 10 –11 cm 3 molecule –1 s –1 ), − in turn, are in good agreement with the results of the temperature-dependent studies.…”

“…In the range of the reported uncertainties on the measurements of k 1 , the current data (T=235-960 K) match very well those from previous study from this group (T=230-360 K), 3 as well as the laser flash photolysis-resonance fluorescence measurements of Ravishankara et al (T=249-416 K) 5 and recently reported results of discharge flow-electron paramagnetic resonance study by Khamaganov et al (T = 298, 370 and 460 K). 24 Three most recent room temperature measurements of the reaction rate constant (reporting the values of k 1 between 0.92 and 1.12×10 -11 cm 3 molecule −1 s −1 ), [25][26][27] in turn, are in good agreement with the results of the temperature dependent studies. Solid line in Figure 3 represents the fit to the present data with sum of two exponential functions: k 1 = 2.53×10 -11 exp(-364/T) + 2.79×10 -13 exp(784/T) cm 3 molecule -1 s -1 Considering that, the present results are in excellent agreement with previous temperature dependent measurements of k 1 , this expression can be recommended to use in the temperature range 230 -960 K with conservative independent of temperature uncertainty of 15%.…”