Temperature dependencies of the Henry's Law constant and the aqueous phase dissociation constant of bromine chloride

Modeling ozone depletion observed in the Arctic troposphere requires mass transport of halogen species between the aqueous and the gas phases, which is proportional to its Henry's Law constant (H-x). UV measurements are made in both the aqueous and gas phases to determine the solubility (H-BrCl = [BrCl(aq)]/[BrCl(g)]RT) of BrCl (279-299 K). The gas-phase absorbance spectrum (330-450 nm, 1 nm intervals) is fit for [BrCl(g)], [Br-2(g)], and [Cl-2(g)], while the absorbance value at 343 nm is used to determine (BrCl(aq)] (and [BrCl2-]). Dissociation (K-aq = [Br-2(aq)][Cl-2( aq)]/BrCl(aq)](2)) data are obtained from K-aq = H(Cl2)H(Br2)Kg/H-BrCl(2) where H-Cl2, H-BR2 and K-g have analogous definitions to H-BrCl and K-aq. Comparison of Henry's Law constants in Table 2 reveals that the order of solubility at 298.2 K is BrCl > Br-2 >> Cl-2. At temperatures relevant to the Arctic, BrCl is much more soluble than Br-2 because of differences in Delta H degrees. Consequently, the relative flux of BrCl from the aqueous to the gas phase should not be as large as that of Br-2 Comparison of dissociation constants in Table 2 reveals the relatively high degree of association of BrCl with H2O molecules in the aqueous phase.