Kinetic studies of reactions of hydrogen atoms with HCl, Cl2 and NOCl, and chlorine atoms with H2 and NOCl

Rate constants for the reaction pair [graphic omitted] have been measured from 295 to 425 K under pseudo-first-order conditions ([HCl]0/[H]0 and [H2]0/[Cl]0≫ 1) using the discharge-flow-resonance-fluorescence technique. The rate constants followed the Arrhenius expressions: kf=(2.01 ± 0.3)× 10–11 exp [–(1790 ± 140)/T], kr=(6.00 ± 0.5)× 10–11 exp [–(2470 ± 100)/T].The ratio of these rate constants agrees with the thermodynamic equilibrium constant, suggesting that the complicating wall effects and secondary H-atom reactions observed in previous discharge-flow studies of these reactions have been eliminated.Similar kinetic studies at room temperature of the reactions: [graphic omitted] gave the rate constants: k2=(1.70 ± 0.26)× 10–11 cm3 molecule–1 s–1, k3=(1.82 ± 0.27)× 10–11 cm3 molecule–1 s–1, k4=(7.2 ± 2.4)× 10–11 cm3 molecule–1 s–1. The values for k2 and k3 are in excellent agreement with those reported by previous discharge-flow–resonance-fluorescence studies. The value for k4 is approximately a factor of two larger than the only other direct determination.