The pressure dependence of the rate constant for the reaction: HO + CO → H + CO2 |
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Authors: | Walter H. Chan William M. Uselman Jack G. Calvert John H. Shaw |
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Affiliation: | Department of Chemistry and Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA |
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Abstract: | Relative rate measurements of the reactions of the HO-radical with CO [HO + CO → H + CO2 (1)] and with isobutane [HO + iso-C4H10 → H2O + t-(or iso-)C4H9 (3)] have been made through the photolysis of dilute mixtures of HONO with CO, iso-C4H10, NO2, and NO in simulated air at 700 and 100 torr pressure and 25 ± 2°C. In situ, long path, FT-IR analysis of the reactants and products provided essentially continuous monitoring of the reactions during the course of the experiments. The kinetic analysis of the data coupled with Greiner's estimate of k3 give new estimates of k1 = 439 ± 24 ppm?1 min?1 in air at 700 torr and k1 = 203 ± 29 ppm?1 in air at 100 torr. The results confirm the recent conclusions of Cox and Sie and their co-workers that the rate constant for reaction (1) is pressure dependent. Modeliers of the chemical changes which occur in the troposphere should adopt a new value for the rate constant k1 which is about a factor of two larger than that in current use by most groups. |
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