Surface Concentrations and Compound Formation in Aqueous Sulfuric Acid

Abstract

The concentration of free water molecules at the surface of a strong sulfuric acid solution is found to be very low, mainly as a consequence of the formation of acid hydrates. Values of equilibrium constants and enthalpy changes for successive hydration reactions of H₂SO₄ have been calculated from the variation of water vapour pressure with acid strength and temperature. The results support the conclusion of Fried et al. that the rate of reaction of a molecule such as N₂O₅ with a sulfuric acid aerosol is controlled by the rate at which the molecule can penetrate into the bulk of the liquid.