Hydrolysis of N₂O₅ on Submicron Sulfuric Acid Aerosols

The kinetics of reactive uptake of gaseous N 2 O 5 on submicron sulfuric acid aerosol particles has been investigated using a laminar flow reactor coupled with a differential mobility analyzer (DMA) to characterize the aerosol. The particles were generated by homogeneous nucleation of SO 3 /H 2 O mixtures. In the H 2 SO 4 concentration range 26.3−64.5 wt % the uptake coefficient was γ = 0.033 ± 0.004, independent of acid strength. For an acid strength of 45 wt % γ was found to decrease with increasing temperature over the range 263−298 K. From this, temperature dependence values of −115 ± 30 kJ/mol and −25.5 ± 8.4 J/K mol were determined for the changes in enthalpy and entropy of the uptake process, respectively. The results are consistent with a previous model of N 2 O 5 hydrolysis involving both a direct and an acid catalyzed mechanism, with uptake under the experimental conditions limited by mass accommodation.