Ion Pair Formation of CoCl2·6H2O and [Co(NH3)5Cl]Cl2 in Aqueous Medium at Different Temperatures-A Conductance Method

Abstract

Conductances of cobalt(II) chloride hexahydrate and pentaamminechlorocobalt(III) chloride has been measured in aqueous medium at 298.15 to 323.15 K. The conductance data in all cases have been analyzed by Shedlovsky equation to obtain limiting equivalent conductance (Λ₀) and association constant (K_A) values for the electrolyte. The limiting equivalent conductance and the ion association constants values for cobalt(II) chloride hexahydrate were found to be higher than those in pentaaminechlorocobalt(III) chloride. Based on the K_A values and temperature dependence of Λ0, the thermodynamic parameters viz., free energy (ΔGº),enthalpy (ΔHº) and entropy (ΔSº) have been determined. Both the associations are exothermic in nature which is determined by negative values of ΔHº. The chosen metal complexes show ion-pair association within experimental different temperature ranges;which is supported by negative values of ΔGº