A kinetics study of the homogeneous and heterogeneous components of the HCl + ClONO_2 reaction

The kinetics of the reaction HCl + ClONO_2 → Cl_2 + HNO_3 were investigated at 298 K using a flow reactor with FTIR analysis to assess the importance of this reaction for stratospheric chemistry. The observed reaction was characteristic of a heterogeneous process; an upper limit of 5 × 10^(−18) cm³ molecule^(−1) s^(−1) was obtained for the homogeneous gas phase rate constant. From calculations of the first order wall rate constant, estimates were made of the reaction rate on stratospheric aerosols. Because both HCl and ClONO_2 need to be adsorbed on the particle surface, the reaction will be of negligible importance under most stratospheric conditions