A discharge-flow study of Cl2O3

Abstract

The discharge-flow technique coupled with UV-absorption spectroscopy has been used to study the production of dichlorine trioxide, Cl₂O₃, from the reaction between ClO and OClO radicals. The absorption cross section of Cl₂O₃ was determined to be (1.44 ± 0.10) × 10⁻¹⁷ cm² molecule⁻¹ at λ_max = 267 nm (all errors reported are two standard deviations of the statistical error). The equilibrium constant for the process ClO + OClO + M ⇌ Cl₂O₃ + M was measured in the temperature range 243–298 K. A Second-Law analysis yielded values of Δ_rH = −57.9 ± 2.1 kJ mol⁻¹ and Δ_rS = −132.6 ± 7.9 J K⁻¹ mol⁻¹. The rate coefficient for the formation of Cl₂O₃ was measured with helium as the third body at a concentration of ∼7.3 ± 10¹⁶ molecule cm⁻³ over the temperature range 243–283 K. Analysis of these data employing the conventional form of the rate equation for the low-pressure limit, k⁰(T) = k⁰(300)·(T/300)⁻ⁿ, resulted in values of k⁰(300) = (2.83 ± 0.04) × 10⁻³² cm⁶ molecule⁻² s⁻¹ and n = −4.32 ± 0.1. These spectroscopic, thermochemical and kinetic data are compared with previously reported values.