Accurate Prediction of Deprotonation and pH value of Acids in Aqueous
Solutions over the Whole Concentration Range
- Bong-Seop Lee
, - Shiang-Tai Lin
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Abstract
The pKa of an acid is important for determining the dissociation and
thermodynamic properties of solutions containing it. However, the value
of pKa is typically determined at dilute limit and cannot be used to
describe properties of the solution at high concentrations. In this
work, we propose an approach to determine the concentration independent
equilibrium constant Keq based on pKa and predicted activity
coefficients. The Keq determined is applied to predict the degree of
dissociation over whole concentration range for weak to strong acids.
The pH of acid aqueous solution is predicted over whole concentration
range, showing a good agreement with experiments. Based on this
approach, we found that the vapor pressures of acid aqueous solutions
strongly depend on the degree of dissociation of acids. The proposed
model provides useful insights to link the macroscopic properties of
acid aqueous solutions to its microscopic dissociation phenomena over
the whole concentration range.