Rate Measurements for the Reaction H + Cl₂ → HCl + Cl by Lyman‐α Fluorescence

Abstract

The rate of the reaction between hydrogen atoms and chlorine has been determined in a discharge-flow system. By use of sensitive detection of H atoms by Lyman-cc resonance fluorescence the reaction could be studied at low initial H atom concentrations and unperturbed by interfering processes. From measurements in the temperature range T = 252 -458 K the Arrhenius expression cm3 k , = (8.7 k 1.7)1013exp(-5.0 & 0,6kJmol-'/RT)-mol s can be derived. Die Geschwindigkeit der Reaktion zwischen Wasserstoffatomen und Chlor wurde in einem Stromungssystem gemessen. Aufgrund des empfindlichen H-Atom Nachweises durch Lyman-cr-Resonanzfluoreszenz konnte die Reaktion bei niedrigen Wasserstoffatomkonzentrationen und unbeeinfluI3t durch storende Nebenreaktionen untersucht werden. Aus Messungen im Temperaturbereich T = 252 -458 K 1aBt sich die Geschwindigkeitskonstante in Arrhenius-Form k l = (8,7 + 1,7) 1013exp(-5,0 + 0,6kJmol-'/RT)* herleiten. mol s

Comparison of rate constants for reactions of hydrogen atoms with chlorine, fluorine, iodine chloride, and chlorine fluoride

“…°The absolute value of the + Cl2 rate constant at room temperature is 2.06 X 10"11 cm3 molecule'1 s'1; average value from ref 5 and 6. 6 Defined as k/(u). c This entry is for the sum of fenci and feHF of reaction III.…”

“…Slightly different probabilities were used by ref 2, 13, and 11 and exact agreement would not be expected on this basis. 6 For each reaction the contribution to v = 0 is taken to be zero. c The distribution listed here is the one that has been corrected for secondary reaction, see Table I of ref 1.…”

“…The fraction of the high J component present a Rate constants are entered on and above the diagonal; macroscopic branching ratios with the least exoergic channel as the numerator, e.g., ^hci^hf for H + C1F are entered below the diagonal. 6 For the HC1 channel only; see branching ratios for upper limit to HI formation. in the lower vibrational states from H + IC1 is listed in Table III.…”

Muonium Chemistry—A Review

“…A number of comments on the data in Table II reaction, the reaction rates have never been measured directly but have been obtained by measurement of ratios of competitive reaction rates. Even the reaction rates that have been measured directly have widely varying reported values; for example, two recent measurements of the H + Q2 reaction (52,53) give room temperature rate constants differing by a factor of four. The source of ambiguity in directly measured reaction rates is competitive interference reactions caused by the presence of several reactive species in relatively large concentration.…”

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

“…(11) and the reciprocal rate constant of the chemical step, assumed to follow the Arrhenius dependence provided by Wagner et al (1976) for the gaseous reactants (see Table 2 for details).…”