Heterogeneous Kinetics of the Uptake of ClONO2on NaCl and KBr

The uptake kinetics of ClONO 2 on NaCl (reaction 1) and on KBr (reaction 2) have been studied in a low-pressure, Teflon-coated Knudsen reactor at room temperature. The initial uptake coefficient for both reactions has been measured as 0.23 ± 0.06 and 0.35 ± 0.06 for reactions 1 and 2, respectively, and is independent of reactant density in the range 10 10 −10 13 molecules cm -3 . The values of the uptake coefficients are independent of presentation of the salt substrates: identical results are obtained on powder, grains, single-crystal surfaces, and thin deposited salt layers. The only product of reaction 1 is Cl 2 . Reaction 2 initially produces Br 2, followed by BrCl and Cl 2 . In our proposed mechanism, BrCl is the product of reaction 2, and secondary reactions between BrCl and the KBr substrate yield Br 2 at short reaction times and Cl 2 under prolonged exposure.