chem-201-chapter-12 - 11/7/11 EDTA Titrations EDTA...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
11/7/11 1 EDTA Titrations A chelating ligand is a molecule, acting as a Lewis base, that attaches to a metal ion Most metal ions can bind six ligands Monodentate ligands attach at only one site on the metal ion Cu(NH 3 ) 4 (NO 2 ) 2 2+ Mo(CO) 6 EDTA Titrations Multidentate ligands attach at two or more sites on the metal ion Cd(C 2 H 8 N 2 ) 2 (H 2 O) 2 2+ EDTA Titrations EDTA = e thylene d iamine t etra a cetic acid (C 10 H 16 N 2 O 8 ) EDTA Titrations EDTA can attach to a metal ion at up to six sites EDTA Titrations In solution, EDTA is a hexaprotic acid, H 6 Y 2+ : H NCH 2 CH 2 N H H OOCCH 2 H OOCCH 2 CH 2 COO H CH 2 COO H + + H are acidic hydrogens pK 1 = 0.0 (carboxylic) pK 4 = 2.69 (carboxylic) pK 2 = 1.5 (carboxylic) pK 5 = 6.13 (amine) pK 3 = 2.00 (carboxylic) pK 6 = 10.37 (amine) EDTA Titrations The completely deprotonated form of EDTA is written Y 4- : NCH 2 CH 2 N OOCCH 2 OOCCH 2 CH 2 COO CH 2 COO + + The fraction of EDTA in the Y 4- form, α Y 4- is: ] EDTA [ ] Y [ ] Y [ ] HY [ ] Y H [ ] Y H [ ] Y H [ ] Y H [ ] Y H [ ] Y [ 4 4 3 2 2 3 4 5 2 6 4 Y 4 + + = + + + + + + = α [EDTA] = concentration of all free EDTA— not complexed to metal ion
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
11/7/11 2 EDTA Titrations The form of EDTA varies as a function of pH pH α Y4- 0 1.3 x 10 -23 1 1.4 x 10 -18 2 2.6 x 10 -14 3 2.1 x 10 -11 4 3.0 x 10 -9 5 2.9 x 10 -7 6 1.8 x 10 -5 7 3.8 x 10 -4 8 4.2 x 10 -3 9 0.041 10 0.30 11 0.81 12 0.98 13 1.00 14 1.00 Figure 12-7 or 11-7 Table 12-1 or 11-1 EDTA Titrations
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 11/17/2011.

Page1 / 3

chem-201-chapter-12 - 11/7/11 EDTA Titrations EDTA...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online