Rate measurements of the hydroxyl radical by resonance absorption. IV. Reactions of the hydroxyl radical with ammonia and nitric acid.
Rate consts. were detd. for the reaction (1) OH + NH3 -> H2O + NH2 between 228 and 472 DegK, and for (2) OH + HNO3 -> H2O + NO3 from 240 to 406 DegK. In the expts. on reaction (1), OH radicals were created by flash photolyzing H2O; in those on reaction (2) .apprx.0.1% of the HNO3 was photolyzed to produce OH. The subsequent removal of OH was, in both cases, followed by measuring the absorption of OH resonance radiation as a function of time. For reaction (1), the results can be expressed in terms of the Arrhenius expression: k1 = 2.3 * 10-12 exp(-1.6 kcal mol-1/RT) cm3 mol-1 sec-1, with a std. deviation of +- 0.03 in log k1. The rate const., k2, varies very little with temp. in the range covered by our measurements. At room temp. and below, k2 = 0.8 (+- 0.2) * 10-13 cm3 mol-1 sec-1.
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