Nitric Acid Oxidations

Kurt was searching for information regarding the fundamentals of HNO3 oxidations. In particular, he wanted to know how to maintain nitric acid's oxidative ability at moderate dilutions.

Dear Kurt,

Thanks for contacting Inorganic Ventures. I have not found a reference on this topic that goes into detail. However, the chemistry of nitric acid is of interest to Inorganic Ventures. The following is my understanding of this chemistry:

There are two reactions that nitric acid follows. In dilute solution the reaction is: NO3- + 4H++ 3e- = NO + 2H2O; E0 = 0.96. Assuming you are working in dilute solution then the expression for ΔE (the reduction potential difference between two half cells) is: (ΔE) = 0.0591/n logK, where ΔE is form the oxidation reduction reaction equation, n is number of electrons, and logK is the equilibrium expression for the reaction.

In addition, the half reaction potential (E) for nitric acid may be estimated using the Nernst Equation, where E = E0 + 0.0591/3log[(H+)4 (NO3-)]/(PNO). This equation predicts an increase in the reduction potential (increase in oxidizing ability) as the acidity and molarity of nitric acid increases. Please keep in mind that this assumes a reaction that is not kinetically limited (irreversible).

Please feel free to call with any questions.

Serving you in chemistry,

Paul R. Gaines, Ph.D.
CEO of Inorganic Ventures & Fellow Chemist

DISCLAIMER: Advice offered by the chemists at Inorganic Ventures is intended for the individual posing the question. Feel free to contact us to verify whether these suggestions apply to your unique circumstances.