The structure of aqueous solutions and the association of electrolytes formed by ions with negative hydration

Solovkin, A.S.

doi:10.1007/bf00744354

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“…This regularity is not explained by nitrate complexing of the reacting ions in the slow reaction stages, since theoretical calculations [27] suggest that nitrate complexes are not present. More likely, is the hypothesis that it is due to changes in activity coefficients of these species when the reaction environment changes from HClO 4 to HNO 3 .…”

Section: Discussionmentioning

confidence: 84%

The kinetics and mechanism of the reduction of neptunium (VI) ions by uranium (IV) ions in nitric acid

Koltunov¹,

Taylor²,

Marchenko³

et al. 2002

Radiochimica Acta

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The rapid reduction of NpO 2 2+ ions to NpO 2 + by U(IV) ions in an aqueous nitric acid solution has been studied and, in many ways, is similar in character to the same reaction in HClO 4 . The major difference is that in HNO 3 the reaction proceeds via two parallel routes. The first is via the hydrolysed UOH 3+ ion, as in the reaction in HClO 4 and the second is via the non-hydrolysed U 4+ ion. These parallel routes lead to the observed order of reaction with respect to H + ions being reduced from −1 in HClO 4 to −0.7 in HNO 3 . After accounting for the reaction mechanism the rate equation is described by:where k 8 = 404 min −1 , k 19 = 275 M −1 min −1 and β = 0.009 M at 10 • C and µ = 2. The activation energy was 66.5 ± 4.9 kJ mol −1 . Nitrate ions had no effect on the reaction rate but sulphamic acid increased the observed rate, probably through catalysis by sulphate ions arising from sulphamic acid reaction with HNO 2 and hydrolysis.

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Section: Discussionmentioning

confidence: 84%