Transcription of Chapter 12 EDTA Titrations - Cal State LA
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Chapter 12 EDTA Titrations - Cal State LA
1 Chapter 12 EDTA TitrationsAcids and Bases Definitions: Lewis Electrons (acid: electron pair acceptor); Br nsted-Lowry (acid: proton donor)Metal ions (electron pair acceptor) Lewis acidLigand (electron pair donor) Lewis baseLewis acid-base concept in Metal-Chelate ComplexesCoordination Number The atom of the ligand that supplies the nonbonding electrons for the metal-ligand bond is thedonor atom. The number of these atoms is thecoordination FormationFormation of coordinate bonds between Lewis Acids/BasesFormation constants (Kf) are the equilibrium constants for complex ion formation. The overall, or cumulative, formation constants are denoted i2122323]][[])([KKNHAgNHAgKf ===++b]][[])([331 NHAgNHAgK++=]][)([])([33232 NHNHAgNHAgK++=)()( (aq))(33aqNHAgNHaqAg+++)()( (aq))()(2333aqNHAgNHaqNHAg+++K1K2)()( (aq)2)(233aqNHAgNHaqAg+++KfGeometriesThe re are two common geometries for metals with a coordination number of four:Tetrahedral & Square planarBy far the most-encountered geometry, when the coordination number is six, is Monodentate ligand: binds to a metal ion through only one atom, , CN- Multidentate ligand or chelating ligand:has more than one ligand donor atoms.
Coordinate Complexes EDTA Complexes • EDTA forms 1:1 complexes with most metals (Not with Group 1A metals) • EDTA complexes are usually stable water soluble complexes with high formation constants • Formation constant, K f, (or stability constant): • K f could have been defined for any form of EDTA [ ] [ ][ ]+ --+ - + « - = 4 4 f 4 M Y ...
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