No abstract

Although the dissolution of copper in nitric acid was the object of numerous investigations, little attention has been paid to the stoichiometry of this reaction. We have found that nitrous acid, HN02, is one of the products, and it plays an important role in the intermediate steps of copper dissolution as well.1 We also found the quantities of HN02 and NO gas produced vary from one experiment to another depending on the conditions and, thus, no definite stoichiometry could be predicted for this reaction. The explanation lies with the specific mechanism: the dissolution of copper in nitric acid takes place at first by the reduction of NO3-to HN02, then after a certain accumulation of HN02, the reduction of HN02 to NO gas at the copper surface becomes the predominant process. During these reduction stages, copper is oxidized simultaneously. The evolved NO gas was found2,3 to react with HNO3 to give HN02:

030ChemInform Abstract has been studied over the concentration range 0.48-1.49 M HNO3 by simultaneous detection of the concentration changes of the reactants, intermediate HNO2 and product (Zn2+) with time. A dissolution mechanism is proposed. The diffusion-controlled dissolution process is of first-order with respect to (Zn) and (HNO2).