Effect of water on the HNO{sub 3} pressure dependence of the reaction between gas-phase HNO{sub 3} and NaCl surfaces
- Univ. of California, Irvine, CA (United States). Dept. of Chemistry
Recent studies indicate that reactions of atmospheric pollutants N{sub 2}O{sub 5} and ClNO{sub 2} on the surfaces of sea salt particles may be a significant source of reactive chlorine-containing species (e.g., ClNO{sub 2} and Cl{sub 2}) in the marine troposphere. These reactions compete with the reaction of nitric acid with NaCl which forms the relatively unreactive HCl. The authors show here that the dissociative adsorption of HNO{sub 3}(g) on NaCl to form NaNO{sub 3}(s) and HCl(g) follows single-site Langmuir adsorption behavior. X-ray photoelectron spectroscopy is also used to show that the amount of strongly adsorbed water on the surfaces of NaCl particles strongly depends on the particle size. Particles of 1--10 {micro}m diameter show large quantities of adsorbed water that remain on the sample up to temperatures of 200 C. Particles in the size range of 500 {micro}m diameter have less, but still easily measurable, amounts of strongly adsorbed water. Water desorbs completely from low defect density NaCl(100) surfaces under vacuum at temperatures well below room temperature. The authors present a model for the recently reported HNO{sub 3} pressure dependence of the reactive sticking coefficient of HNO{sub 3} on NaCl under steady-state reaction conditions. The origin of the pressure dependence in the model is the competition between site blocking on the surface by the build-up of the NaNO{sub 3} reaction product and the water-induced 3-D recrystallization of the NaNO{sub 3} that frees up reactive sites for further reaction.
- OSTI ID:
- 682163
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 25 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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