Temperature dependence of the rate constant for hydrogen atom reaction with Cl2−• in water by pulse radiolysis of aqueous HCl solution

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)×10 9  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 • +Cl 2 , 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 • +H 2 O) in water at 25 °C is overestimated by at least two orders of magnitude.