Hydration thermodynamics and hydrodynamic (Stokes) radius of the lanthanide ions

Abstract

Biochemical and physiological properties depend on the size of ions and the thermodynamic quantities of ion hydration in numerous states. The diffusion coefficient (D) of lanthanide series ions (Ln+3) in solution (1.558-1.618 ×10−9 m2 s−1) as calculated by the Einstein–Smoluchowski relation depended on conductance measurements as electro - analytical measurement. The association constant (KA) of Ln+3 ions (210.3-215.3 dm3 mole-1) was calculated by using the Shedlovsky method, and the hydrodynamic radius was (1.515-1.569 ×10−10 m) as calculated by Stokes–Einstein equation. ΔHo, values were obtained from the literature. The thermodynamic functions (ΔGo, ΔSo) were calculated by suitable equations, ΔGo, for ion hydration, had negative values in the range (13.25 - 13.31 kJ/mole), ΔSo also were of negative values, results have been shown in the limit (11.299 - 12.573 kJ/ K. mole).