• Bulletin of the Korean Chemical Society
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• 제26권4호
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• pp.614-618
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• 2005

The complex of the composition LaL(N$O_3)_3\;(H_2O)_2$ is prepared by the reaction of La($NO_3)_3{\cdot}6H_2O$ with Nethylmorpholine in aqueous medium. The ligand is involved in the complex as a neutral species where the chelation occurs via the oxygen of the ligand moiety and the nitrate groups as bidentate ligand. The chemical structure of the studied complex is confirmed through IR, XRD, and thermal analysis data. The complexation equilibria of La(III) with N-ethylmopholine is studied in aqueous medium at ionic strength I = 0.1 mol${\cdot}dm^{-3}\;KNO_3$ and at 25, 35 and 45 ${^{\circ}C}$, respectively. The thermodynamic parameters $\Delta$G, $\Delta$H and $\Delta$S values were calculated to prove the association with the complex formation. It is clearly observed that the process is accompanied by absorption of heat, i.e. endothermic process, while the entropy does not change greatly attributed to the release of constant number of water molecules during chelate formation.