Reduction of Np(VI) with Carbohydrazide in a Perchloric Acid Solution

Resumo

The stoichiometry of the reaction of Np(VI) with carbohydrazide (NH₂NH)₂CO in a 0.02 M HClO₄ solution was studied by spectrophotometry. With Np(VI) taken in excess, 1 mol of carbohydrazide reduces 5 mol of Np(VI) to Np(V). In 0.1−2.0 M HClO₄ solutions (the ionic strength of 2.0 was supported by adding LiClO₄) containing 3–100 mM (NH₂NH)₂CO, Np(VI) at a concentration of 1 mM at 20-45°С is consumed in accordance with a first-order rate law until less than 0.2 mM Np(VI) remains. Then the reaction decelerates. The reaction is first-order with respect to carbohydrazide and has the order of −1.45 with respect to Н⁺ ions. The activated complex is formed with the loss of 1 and 2 Н⁺ ions. The activation energy is 86 ± 5 kJ mol⁻¹.