A model for reversible mass transport of HO2 between the gas and aqueous phases of liquid water clouds is used to examine the coupling of reaction kinetics of this species in the two phases. The Henry's law coefficient of HO2 necessary for this analysis is evaluated by means of a thermochemical cycle involving O-2(aq) to be (1--3)¿103 M atm-1. The mass accommodation coefficient α for uptake of HO2 by liquid water is not known and is treated as an adjustable parameter. Results are expressed in terms of yields of HNO3(g),H2O2(aq) relative to the initial photochemical generation rate of OH(g). For large values of α(>10-3) aqueous-phase H2O2 formation may be a major radical sink process, but the rate of aqueous-phase H2O2 production decreases strongly with α≲10-3. Substantial difference, e.g., a factor of as much as 50 in gas-phase HO2 concentraiton, is found between kinetic calculations where uptake of HO2 by cloud droplets is treated reversibly versus irreversibly. Such differences demonstrate the need to treat the dissolution process as reversible, even for reactive free-radical species.