Kinetics of the bromate–bromide reaction at high bromide concentrations

At bromide concentrations higher than 0.1 M, a second term must be added to the classical rate law of the bromate–bromide reaction that becomes −d[BrO 3 − ]/d t = [BrO 3 − ][H + ] 2 ( k 1 [Br − ] + k 2 [Br − ] 2 ). In perchloric solutions at 25°C, k 1 = 2.18 dm 3 mol −3 s −1 and k 2 = 0.65 dm 4 mol −4 s −1 at 1 M ionic strength and k 1 = 2.60 dm 3 mol 3 s −1 and k 2 = 1.05 dm 4 mol −4 s −1 at 2 M ionic strength. A mechanism explaining this rate law, with Br 2 O 2 as key intermediate species, is proposed. Errors that may occur when using the Guggenheim method are discussed. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 17–21, 2007