Evaluation of association constant and thermodynamic parameters of [Cu(Me-AAUH)2]Cl2 complexes in aqueous medium

Conductance measurements on aqueous solutions of bis-methyl 1-amidino-O-methylurea copper (II) chloride and bis-methyl 1-amidino-O-ethylurea copper (II) chloride have been investigated at different temperatures ranging from 25 – 50 0 C over wide range of concentration from 1.13-1.80x10-3N. The limiting molar conductance (Λ0) data and ion association constants (KA) values were estimated by analyzing conductivity data in term of Shedlovsky technique. The values of Λo for the electrolytes increase invariably with increase in temperature in aqueous medium, indicating less solvation or higher mobility of ions. This is due to the fact that the increase thermal energy results in bond breaking and leads to higher frequency and higher mobility of the ions as well as KA. The higher KA values in the case of [Cu(Me-AMUH)2]Cl2 compared to [Cu(Me-AEUH)2]Cl2 may be ascribed to the more coulombic type of interaction (specific short-range interaction) between the [Cu (Me-AMUH)2]2+ ion and Chloride ion. The thermodynamic parameters viz., changes in enthalpy (ΔH0), entropy (ΔS0) and free energy (ΔG0) were estimated from the temperature dependence of the ion association constant

Author(s): N. Mohondas Singh, Reuben Lalnuntluanga and Lalzawnpuia

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