Chemical Studies in Shock Waves

Year: 1956

DOI: 10.7907/TQXE-RK75

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.

Shock waves in argon bearing about one percent nitrogen pentoxide vapor have been used to initiate the rapid decomposition of N2O5 between 450[degrees] and 1100[degrees]. The important intermediate in the reaction is the nitrate radical, NO3, whose characteristic absorption bands in the green and red are known. These bands have been identified in flash absorption spectrograms, and quantitative photoelectric measurements of absorption by NO3 have followed its appearance and disappearance in the reaction mixture. Simultaneous measurements with violet light have recorded the production of NO2.

The first step in N2O5 decomposition is: [...]. Near 500[degrees]K, the forward rate and the equilibrium in this reaction have been measured. Above 600[degrees]K, the dissociation is rapid and complete, and the rates of the bimolecular decomposition reactions [...] and [...] have been measured. The contributions of these steps have been established by experiments in the presence of excess NO2. The reaction [...] is fast, and although NO2 is unstable with respect to NO and O2 above about 600[degrees]K, the stoichiometric reaction [...] has been observed in the short times of these experiments. The rate equations and the constants and energies measured agree very well with predictions based on mechanisms known at room temperature.

Two papers on the rate of dissociation of molecular iodine, by the present author and others, are included. The abstracts accompanying these papers are on pages 118 and 131.