The Kinetics of Oxidation of Iodide ion by Dichromate Ion in an Acidic Medium

The kinetics of dichromate-iodide reaction in an acidic medium was studied by iodometric technique. The rate has been studied by appropriate choice of concentration conditions at constant temperature and ionic strength. The kinetic studies showed half order reaction with respect to dichromate ion and first order both for iodide ion and hydrogen ion concentrations.

The observed rate law is given:

d[l₂] = K[Cr₂O₇^2-]^½ [I^-][H⁺]

dt

The value of the rate constant was 8.67mol^½ S² L^-½

The dependence of reaction rate on temperature was monitored and Ea, A, ΔS, ΔH and ΔG were evaluated to be 20.30 KJmol^-1, 2.0x10¹², 24.38 KJmol^-1, 43.56 KJmol^-1 and -32.30 KJmol^-1 respectively, which implies that the reaction is spontaneous with negative value of ΔG, and Exothermic.