Viscosities of ammonium salts in water and ethanol + water systems at different temperatures

Abstract

Viscosities of different concentrations of ammonium chloride and ammonium bromide from 1 × 10 − 2 to 9 × 10 − 2 mol dm − 3 solutions in aqueous and aqueous alcoholic (10% v/v ethanol) mixtures were measured at temperatures ranging from 298 to 323 K respectively. It was observed that the viscosity of solution increased with the increase in the concentration of salts (ammonium chloride and ammonium bromide) in aqueous system and decreased in aqueous ethanol system. The viscosity data were used to evaluate ion–ion interactions and ion–solvent interactions in terms of ‘ A’ and ‘ B’ coefficients of Jones–Dole equation respectively. The positive values of B-coefficient for ammonium chloride and ammonium bromide in aqueous system indicate that ammonium chloride and ammonium bromide behave as structure maker in aqueous system while in aqueous ethanol system structure breaking behaviour was observed. With the help of viscosity data, the activation parameters such as energy of activation ( E η), free energy change of activation (Δ G⁎) and the entropy change of activation (Δ S⁎) were evaluated as a function of salt concentration, solvent composition and temperature.