Kinetic investigations of the iodate-iodide reaction in neutral solution

Abstract

A non-buffer pH-stat method is used for kinetic investigation of the iodate-iodide reaction in neutral pH region. For [I-] and [IO3-] of the order of 10-2M (M = mol. dm-3) and [H+] approximately 10-7M, the rate of reaction between iodate and iodide was found to be fourth order in iodide ion and second order in iodate ion. The order with respect to hydrogen ion showed an increase from first towards third as the hydrogen ion concentration decreased. The experimental data fitted the empirical expression at 25°C, I = 1.00 M (v = reaction velocity, t = time, I = ionic strength)over the experimental range covered for k0 = 3.0x10 8 M-4 s-1 and k1 = (8±5)x10 10 M-6.5 s-1. Possible reaction paths are considered. A critical evaluation of the experimental method is included.