Kinetics of the Reduction of Selenious Acid by Sulfur Dioxide. I. Reduction in Acidic Solution with Hydrochloric Acid

Abstract

Abstract (1) The reduction of selenious acid in hydrochloric acid by sulfur dioxide is a typical second order reaction with respect to selenious acid, while the reaction is of zero order with respect to sulfur dioxide because of the continuous passage of sulfur dioxide through a solution. (2) The results obtained at 70, 60, 55 and 50°C (a=0.0184 mol./l., [H+]=0.49g. ion/l.) give a good Arrhenius plot, leading to the value of 24.5 kcal. mol−1 for the energy of activation. (3) The rate constant of this reaction under a certain condition can be evaluated by the general equation, k 1=2.054×1015×[H+]2exp(−E⁄RT) where [H+] is hydrogen ion concentration, E, the energy of activation and T absolute temperature. (4) The reduction of selenious acid in sulfuric acid, which will be published in a subsequent paper, is a reversible reaction. The above equation for the rate constant is utilized as a basic equation, in order to determine the rate constant in the forward direction of the reversible reaction.