Determination of stoichiometries and stability constants of chromium complexes with some nitrogen-containing ligands

Abstract

The work outlined in this thesis includes the preparation and analyzation of Cr3+ with two nitrogen-containing ligands , ethanolamine and diethylamine , for determination of stiochiometries and stability constants of the chelates and the factors that effect the formation of the chelates such as temperature,pH and time .The dissociation constants of the ligands were calculated and compared with that recoreded in literature . Two methods were adopted the pH-metric method and spectrophotometric method . The result is that ethanolamine formed chelates 1:1 and 1:3 with Cr3+ ion and the study have been done with two above methods ,the stability constants was in order K1< K3 , that indicates chelate 1:3 is more stable than chelate 1:1 . Diethylamine ligand with Cr3+ ion formed complexes 1:2 and 1:3 , the stability constants for complexes were calculated by pH-metric method and spectrophotometric method , the result found is in the order K2 < K3 , what indicates complex 1:3 is stabler than complex 1:2 . The study shows that he stability constant ( K3) for diethyamine chelate with Cr3+ is greater than ( K3) for ethanolamine chelate with Cr3+ for diethylamine is more alkaline than ethanolamine . In this task the effect of some external factors such as pH , temperature and the time have been studied and the influence of these parameters has been recorded .