A Kinetic Study of the Oxidation of Iron (II) by Chlorine

Author: Crabtree, James Hansen

Year: 1965

Degree: Bachelor's thesis

Advisors: Schaefer, William P.; Davidson, Norman R.

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/0frx-wx53

Abstract

The kinetics of the oxidation of iron (II) by aqueous chloring has been investigated spectrophotometrically at an ionic strength of 1.00 M. In solutions with [H+] = 0.05 - 1.00 M, [Cl-] = 0.10 - 1.00 M, [Fe++] = 10-5 - 10-4, [Cl2] = 10-5 - 10-4 M, [Fe+++] 0 = 0.00 - 10-4 F, the rate law is d [Fe+++] / dt = k1 [Fe++] [Cl3-] + k3 [Fe++] [Cl2] ; k1 = 1510 (± 150) M-1sec.-1, k3 = 316 (± 30) M-1sec.-1, and R25/ [Fe++] [Cl2] = 109.47 exp (-9.320/RT). There is no apparent ferric inhibition of the reaction and the data suggest an iron (IV) intermediate. Small amounts of copper (II) catalyse the reaction and the data suggest a mechanism involving a copper (I) intermediate, since ferric ion inhibits the reaction. In solutions with [H+] = [Cl-] = 1.00 M, [Fe+++]0 = 0.00 - 4.40 X 10-5 M, and [Cu++]0 = 10-6 - 10-4 M, the data are consistent with the additional rate term: k11[Fe++][Cu++] (1/1 + k12[Fe+++] /k14[Cl2] k11 = 370 (± 20) M-1sec.-1, and k12/k14 = 0.14 (± 0.02) at 30.0°.

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