Homogeneous isotope exchange reactions. Part 3.—H2S + D2

Abstract

The kinetics of the early stages of the exchange reaction in H₂S + D₂ mixtures [H₂S, 0.55–9.34 Torr (1 Torr = 133 N m^–2); D₂, 0.55–6.39 Torr] have been studied in a static system at 808–937 K. The effects of excess argon and surface to volume (s/v) ratio were studied. The initial rate is independent of s/v and in the absence of Ar is described by d[HDS]/dt=k[H₂S][D₂]^½, where log₁₀(k/dm mol^–½ s^–1)= 12.10 ± 0.25–(11 860 ± 220)†/(T/K). The results are in agreement with a homogeneous radical chain mechanism, initiated and terminated heterogeneously. The rate constants for H + H₂S [graphic omitted] HS˙+ H₂, HS˙+ D₂ [graphic omitted] HDS + D, deduced are log₁₀(k₃/dm³ mol^–1 s^–1)= 10.44 ± 0.25–(330 ± 220)/(T/K), log₁₀(k₆/dm³ mol^–1 S^–1)= 10.13 ± 0.25–(3530 ± 220)/(T/K).