Reaction between hydrogen and nitrous oxide

Abstract

The slow reaction between H₂ and N₂O has been studied in detail at 540 and 600°C. The order in H₂ is effectively zero at both temperatures and the order in N₂O is 1.2 ± 0.2. Addition of helium increases the rate very slightly at H₂= N₂O = 100 Torr, but a greater effect is observed as the pressue of reactants decreases. Termination at the vessel surface, and by gas-phase recombination of H atoms can be eliminated, and is considered to occur through the reaction sequence (7), which competes with the propagation reaction (3), followed by (8). H + N₂O→OH + N₂(3), H + N₂O→NH + NO (7), NH + N₂O→HNO + N₂. (8). Possible reactions of HNO considered are: H + HNO→H₂+ NO (9), OH + HNO→H₂O + NO (10), HNO + HNO→H₂O + N₂O (12), HNO + M→H + NO + M (13), HNO + NO→OH + N₂O. (14). The occurrence of (7) is confirmed by the detection of NO in small yield; the existence of a maximum in the [NO], time profile indicates that (12) is the dominant reaction of HNO, though some contribution from (14) and from either (13) or (9), or both, is required. The inhibiting effect of NO is attributed to reaction (11) and computer treatment shows that both the NO-inhibited rates and the [NO], time profile can be accurately interpreted. Although a unique set of rate constants cannot be obtained, a number of the rate constants can be located within fairly precise limits. H + NO + M→HNO + M. (11)