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Equilibrium Constant of the Reaction OH + HNO3 } H2O + NO3 in Aqueous Solution



G A. Poskrebyshev, Pedatsur Neta, Robert E. Huie


The equilibrium reaction OH + HNO3 } H2O + NO3 was investigated by pulse radiolysis in aqueous solutions. An estimate of the equilibrium constant was derived from the dependence of the absorbance of NO3 radicals upon [HNO3] and estimates of the forward and reverse rate constants were obtained from the dependence of the formation rate constant on the ratio of the activities of nitric acid and water. Studies were carried out at different values of the dose per pulse and different pH values. These observations were modeled, taking into account all relevant reactions for the formation and decay of the nitrate radical. From these modeling studies, the estimated rate and equilibrium constants were refined. The rate constant of the forward reaction is found to be (8.6 1.3) x 107 L mol-1 s-1, the rate constant of the reverse reaction (3 1) x 102 L mol-1 s-1, and the equilibrium constant Keq = (2.8 0.4) x 105, all at zero ionic strength. From the latter value of Keq and taking Eo(H+, OH/H2O) = 2.72 V vs NHE we calculate the reduction potentials Eo(H+, NO3/HNO3) = (2.40 0.01) V and Eo(NO3/NO3-) = (2.48 0.01) V.
Journal of Geophysical Research
106 No. D5


hydroxyl radical, kinetics, nitrate radical, pulse radiolysis, reduction potential


Poskrebyshev, G. , Neta, P. and Huie, R. (2001), Equilibrium Constant of the Reaction OH + HNO<sub>3</sub> {} H<sub>2</sub>O + NO<sub>3</sub><sup> </sup> in Aqueous Solution, Journal of Geophysical Research (Accessed April 24, 2024)
Created February 28, 2001, Updated October 12, 2021