Gaseous Product Identification and Temporal Analysis of Heterogeneous Reactions of Alkali Chlorides with HNO3 Solutions

Waves Cafeteria

Chlorine chemistry in the troposphere, the region of the atmosphere where we live and breathe, is significant in the formation of smog, including ground level ozone. Chloride in sea salt droplets, injected into the atmosphere through ocean wave action, reacts with nitrogen-containing pollutants emitted during fossil fuel combustion to create chlorine-containing gases including Cl₂ and ClNO. These gases quickly split apart in sunlight forming chlorine atoms, which are powerful initiators to the complex chain of reactions forming ozone and other secondary pollutants. This investigation identified and quantified Cl₂, HCl, ClNO, NO₂, and other gases evolved during solid-liquid reactions of chloride salts with aqueous nitric acid, HNO₃. Utilizing multicomponent Beer’s law analyses incorporating single wavelength UV-Vis and integrated IR absorption cross-sections, Cl₂, HCl, ClNO, NO₂, and other product gases were monitored as they formed over time using a custom glass reactor fitted inside UV-Vis and IR spectrophotometers. Temporal studies are indicative of a two-step mechanism with the major products Cl₂ and ClNO formed in nearly equimolar amounts. The relevance of these findings to the chemistry of the polluted troposphere will be discussed.