New Modeling of Nitric Acid Dissociation Function of Acidity and Temperature

Abstract

Nitric acid is widely used for many applications. However, because of the large number of nitrogen species and the fact that for concentrations greater than 10 –2 mol·L –1 , its dissociation is incomplete in an aqueous medium, nitric media are very complex to describe especially in temperature. Using data from the literature and some nitrous acid analyses, it was possible to determine the balance sheet of all different aqueous nitrogen species for a total nitric acidity ranging from 1.5 to 8.5 mol·L –1 and for temperature ranging from 50 to 95 °C with the assumption that the use of a refrigerant column makes gaseous species negligible. For this, it was necessary to determine the ionic, molecular, and solvent activity coefficients and then solve an eight equation system with nine unknowns by determining one unknown experimentally.

First‐principles study on the plutonium ions interaction with diamide molecules in acid solutions

“…As one can see in Figure 5, the part of the hydrogen atoms was coupled with water molecules forming the hydronium (oxonium) H 3 O + ions, whereas some of hydrogen atoms were combined with nitrate groups forming the neutral HNO 3 molecules. The presence of neutral HNO 3 molecules in our optimized systems was in agreement with the experimental results of Ziouane and Leturcq [40] showing that in the nitric acid concentration of 50% and higher, more than one fourth of the nitrate groups existed as the neutral HNO 3 molecules. In our simulations, the formation of these molecules took place in the peripheral region of optimized systems, where there was no competition between nitrate groups and water molecules to couple with the free hydrogen atoms.…”

Effects of Wet Chemical Oxidation on Surface Functionalization and Morphology of Highly Oriented Pyrolytic Graphite

“…It is unclear if the influence of undissociated HNO3 or the NO2 + itself is causing the observed changes of the HOPG surface in our AFM images. Albeit, the changes in the morphology correspond to the well-known decrease in the fraction of dissociation of HNO3 84,85,100.…”

“…This may imply that at low concentrations, the NO3and HNO3 are tied up with hydrogen bonding with water and may have less of an impact on the etching of the HOPG surface. Although NO2 + was not observed, it could be present in low concentrations (predicted as 1.0 x10 -7 M in 8.0 M HNO3 solutions) from the self-ionization of HNO3 and the enhanced hydrogen bonding of other ions at high HNO3 concentrations 100. If NO2 + concentrations exist in solution, they could react on atomic defect sites86,102,103 (shown in FigureS5in the supporting information) and contribute to the large trenches observed in the AFM images in Figure6D-F. Further explanation is given in the supporting information.…”

Effects of Wet Chemical Oxidation on Surface Functionalization and Morphology of Highly Oriented Pyrolytic Graphite

“…Although NO2 + was not observed, it could be present in low concentrations (predicted as 1.0 x10 -7 M in 8.0 M HNO3 solutions) from the self-ionization of HNO3 and the enhanced hydrogen bonding of other ions at high HNO3 concentrations. 100 If NO2 + concentrations exist in solution, they could react on atomic defect sites 86,102,103 (shown in Figure S5 in the supporting information) and contribute to the large trenches observed in the AFM images in Figure 6D-F. Further explanation is given in the supporting information. It is unclear if the influence of undissociated HNO3 or the NO2 + itself is causing the observed changes of the HOPG surface in our AFM images.…”

“…Albeit, the changes in the morphology correspond to the well-known decrease in the fraction of dissociation of HNO3. 84,85,100…”