Kinetic Study of the Reduction of Ferric-1, l0-orthophenanthroline with Uranium (IV) EDTA

The kinetics and mechanism of the reduction of ferric 1,10 arthophenanthroline by Uranium (IV) ethylenediammine tetra acetate  was investigated in aqueous hydrochloric acid   at 25°C, ionic strength 0.01 mol dm-3 and pH 3.5. Rate law for the formation of Fe (II) opt was established through spectrophotomeiric  measuresed   at constant and varying pH by isolation method. At pH of 3.5 and temperature of 25°C, the order of reaction    was found to be second having the value of 221    M-1 mind   and   rate law is suggested    to be   d/dt [Fe(opt)3 ]+2 = K1 [U(IV) EDTA H+ } [Fe(opt)3 ]+3. Differed thermodynamic functions for the reaction were Ea= 3.37 KJ mol-1, DG = -42     KJ mol-1, DH-2 KJ mol-1and DS =148 J K4 mol-1. At different pH values the rate law  was observed as rate = Kk1[H+]  [ U(IV) EDTA ] [Fe(opt)3 ]+2, where K is equilibrium constant for the reaction [U(IV) EDTA] + [H+] - [ U(IV) EDTA H+ ] and k1 is the specific rate   constant for  the reaction  [U(IV)EDTA H]+   + [Fe(opt)3]3+® [U(V)EDTA]  + [Fe(opt)3]2+.

M QADRI ,M A FARRUKH ,I I NAQVI ,