Hydrolysis of N2O5 on submicron sulfuric acid aerosols

The kinetics of reactive uptake of gaseous N2O5 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 SO3/H2O mixtures. In the H2SO4 concentration range 26.3-64.5 wt % the uptake coefficient was gamma = 0.033 +/- 0.004, independent of acid strength. For an acid strength of 45 wt % gamma 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 N2O5 hydrolysis involving both a direct and an acid catalyzed mechanism, with uptake under the experimental conditions limited by mass accommodation.