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

Published

March 1, 2001

Author(s)

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

Abstract

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 K_eq = (2.8 0.4) x 10⁵, all at zero ionic strength. From the latter value of K_eq and taking E^o(H⁺, OH/H₂O) = 2.72 V vs NHE we calculate the reduction potentials E^o(H⁺, NO₃ /HNO₃) = (2.40 0.01) V and E^o(NO₃ /NO₃^-) = (2.48 0.01) V.

Citation

Journal of Geophysical Research

Volume

106 No. D5

Pub Type

Journals

Keywords

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

Citation

Poskrebyshev, G. , Neta, P. and Huie, R. (2001), Equilibrium Constant of the Reaction OH + HNO₃ {} H₂O + NO₃ in Aqueous Solution, Journal of Geophysical Research (Accessed October 31, 2024)