Effect of Temperature on Ion-Exchange Equilibria in Mixed Solvents : Part I-Alkali-Hydrogen Exchange in Aqueous Acetone on Dowex-50w x-8.

School of Studies in Chemistry, .Tiwaji University, Gwalior Manuscript received 5 February 1974; accepted 6 August 1974 The equilibrium constants for alkali-hydrogen exchanges on Dowex —50W X-8 (a sulpho­nated copolymer of styrene and divinyl benzene, 8%) in aqueous acetone solutions have been determined at temperatures 25°, 35° and 45°. The equilibrium constants (thermodynamic) have shown an increase with increase in temperature, as well as with acetone percentages. The ther­modynamic functions ΔF°, ΔH° and ΔS° have been evaluated for exchanges under study for each mixed solvent system used. The variability of equilibrium constants leading to selectivity changes with temperature in these mixed solvents have been shown to be controlled by entropy (ΔS°), changes, while ΔS° variations are influenced by (a) ion-pair interactions and (b) disturbances in hydration spheres of metal ions. The free energy of exchange (ΔF°) decreases with increasse in organic solvent concentration