Abstract

Humayun Kabir¹, Ranjit K. Nath², Kamrul Hossain³ and M. K. Mohammad Ziaul Hyder²

DOI : http://dx.doi.org/10.13005/ojc/340122

Molar Conductance of benzoic acid 1-propanol-water mixtures has been measured in the composition of 0, 5, 10, 15, 20, 30 and 40 wt% of 1-prpanol at 5K interval from 298.15 to 313.15K. The limiting molar conductance Λ_o and thermodynamic dissociation constantpK_a was estimated from the measured conductance data using Bray-Kraus and Fuoss-Kraus equations. An approximate linear dependence of pK_a with the reciprocal of the dielectric constant of the media was observed and this trend may be due to the dominating effect of the coulombic forces of attractions between the opposite ions over the other types of attractions. The gradual decreases of Λ_owith the increase of 1-propanol fraction in the binary mixtures of 1-propanol and water may be attributed to relative increase in the viscosities of 1-propanol-water mixtures. The Walden product and normalized Walden product (nwp) of the benzoic acid in the seven binary mixtures have been calculated and a qualitative proposal has been made regarding their variation with wt% of 1-propanol. The free energies of transfer ∆G°_tr, also have been computed for the acid in the solvent mixtures. The change of pK_a with the solvent composition has been discussed in terms of the free energy of transfer from water to the 1-propanol-water mixtures.

Binary Solvent; Benzoic Acid; Thermodynamic Dissociation Constant

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