Thermodynamic dissociation constants (Ka) of propionic acid in 0, 5, 10 and 20 wt% 1-propanol-water binary mixtures have been determined between 303.15 and 323.15 K. A conductometric method has been applied to measure the molar conductance of dilute solutions of propionic acid. Fuoss-Kraus conductance equation has been applied to calculate the values of limiting molar conductance (Λ0) and thermodynamic ionization constant (Ka). It was found that both the values of Ka and Λ0 decreased by the increasing of amount of 1-propanol in the binary mixtures. However, Ka values were decreased and Λ0 values were increased by increasing temperatures. The normalized Walden products of the propionic acid have been calculated. Thermodynamic quantities such as change of standard free energy (∆G°), change of standard enthalpy (∆H°) and change of standard entropy (∆S°) have been calculated in case of each of the binary mixtures.

A. K. M. Atique Ullah, Mahmuda Akter and Shakhawat Hossain Firoz