Kinetics and Stoichiometry of the Reduction of 2, 6-Dichlorophenol Indophenol with Sulphite Ion in Aqueous Medium

The reduction of 2,6-dichlorophenol indophenol (DCPIP) by sulphite ion in aqueous medium under pseudo-first order condition was studied at ionic strength (I) 0.20 mol dm -3 (NaCl), T= 28±1°C and λ max of 600 nm. The stoichiometry showed that one mole of DCPIP was consumed by one mole of sulphite ion. The reaction was first order with respect to DCPIP, Zero order with respect to sulphite ion and first order overall. The reaction was insensitive to change in ionic strength of the reaction medium and added ion showed catalysis of reaction rate. The overall reaction conform to the rate law d[DCPIP] = k 1 [DCPIP] dt Evidences in this paper showed that the reaction occurred through the outer-sphere mechanism.