Temperature dependence of the rate constant for hydrogen atom reaction with Cl 2 −• in water by pulse radiolysis of aqueous HCl solution

Abstract

Abstract The temperature dependence of the rate constant for the reaction of dichloride anion radical ( Cl 2 - • ) with atomic hydrogen (H•) in water up to 75 °C has been determined by pulse radiolysis of deaerated 0.1 M HCl solution. The room temperature value is (6.1±0.6)×109 M−1 s−1. The activation energy of (13.2±0.6) kJ mol−1 is less than 16.7 kJ mol−1, expected for the diffusion-controlled reaction. Based on the temperature dependence of the rate constant for the reactions H•+ Cl 2 - • and H•+Cl2, derived in this work, and on that reported earlier ( Szala-Bilnik et al., 2014 ) for Cl 2 - • + Cl 2 - • , we show that a value of (10±2) M−1 s−1 determined by Hartig and Getoff (1982) for k (H•+H2O) in water at 25 °C is overestimated by at least two orders of magnitude.