The reaction of indium(I) with iron(III), InI+ 2FeIII→ InIII+ 2FeII, has been studied in air-free conditions µ= 0·7M(LiClO4). Variation of the hydrogen-ion concentration was limited to the range [H+]= 0·01–0·04M in order to reduce the effectiveness of the reaction of indium(I) with H+-ions. The data obtained fit the rate law, –d[FeIII]//dt= 2k1ka[InI][FeIII]//[H+] where k1 is the rate constant for the reaction of In+ with FeOH2+, and Ka is the first acid dissociation constant for Fe3+. At 25°k1= 1·1 × 103 l mol–1 s–1, ΔH1‡= 6·2 ± 0·6 kcal mol–1 and ΔS1‡=–23 ± 2 e.u. With iodine (present as I3–) the reaction, InI+ I3–→ InIII+ 3l–, is too fast to follow using the stopped-flow technique (k2 > 2 × 108 l mol–1 s–1 at 10°). The stoicheiometry of this reaction is 1 : 1 even with [H+]= 2·0M. Formation of a red precipitate of lnl (k3∼ 3 l mol–1 s–1 at 10°) is observed when an excess of indium(I) is used. The reaction of indium(I) with oxygen has been studied at [H+]= 0·0025M. Assuming a first-order dependence on [O2]k4= 1·7 × 103 l mol–1 s–1, at 10° and µ= 0·0025M.
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