Raman spectroscopic study of nitronium ion formation in mixtures of nitric acid, sulfuric acid and water
Abstract
Quantitative Raman spectroscopic measurements of the intensity of the ν(NO) symmetric stretching band of NO2+ in aqueous solutions of nitric and sulfuric acid mixtures have been carried out over the temperature range 293–313 K. From the spectroscopic data it was found that the NO2+ species concentration decreased with an increase in temperature. Equilibrium constants for the reaction HNO3+ 2H2SO4⇌ NO2++ H3O++ 2HSO4– were determined at 293 and 313 K and the average enthalpy of NO2+ formation was found to be ΔH=–25 ± 5 kJ mol–1.