Kinetic study of redox reaction between diphenylbenzidine and thiosulfate

Department of Chemistry, University of Karachi, Karachi-75270, Pakistan

E-mail: abida2020@yahoo.com

Manuscript received 15 March 2004, revised 28 July 2004, accepted 23 August 2004

The kinetics of the redox reaction between diphenylbenzidine (DPB) and thiosulfate was investigated in the range pH 2.0 to 4.5. Order of reaction with respect to thiosulfate, diphcnylbenzidine and H⁺ was found to be one.

The following rate law is recommended :

Rate= k₁ [DPB] [S₂O^2-₃] + k₂ K {DPB [H⁺]} [S₂O^2-₃]

where k₁, k₂ are the rate constants for the reaction

[DPB] + S₂O^2-₃  →  [S4O^2-₆]    +   Product

having the values of k₁ = 5.557 x 10³ dm³ mol^-1 s^-1 and k₂ = 5.827 x 108 dm³ mol^-1 s^-1

K is the protonation constant of DPB having value of 476 dm³ mol^-1.