Vapour Pressure Study of Deuterium Exchange Reactions in Water-Ethanol Systems: Equilibrium Constant Determination

Abstract

A method is proposed for the determination of the equilibrium constants of liquid-phase deuterium exchange reactions from vapour pressure measurements. It is applied to water-ethanol systems to give the equilibrium constant of the reaction 2C2H5OH(l) + D2(l) → 2C2H5OD(l) + H2O(l) The value obtained, 1.05+0.02 at 298 K, is significantly greater than the 'random' value and is more precise and reasonable than a recent calorimetric estimate. Vapour pressures at 298.14 K are reported for the systems H2O+C2H5OH, H2O+C2H5OD, D2O + C2H5OH and D2O + C2H5OD. Molar excess Gibbs functions are obtained from these vapour pressure measurements.