Complexometry volumetric  Volumetric analysis that involve the complex formation of titrate and titrant reaction in aquous media

Examples:  Reaction between silver ion with cyanide ion: Ag + + 2CN - Ag(CN) 2 -  Reaction between calsium ion with EDTA  Ca 2+ + EDTA Ca-EDTA + 2H +

Complex formation  Centre atom/ion : metal ions  Ligand  Electron pairs donor  Electron pairs acceptor  Coordination number

Examples Metal ions Ligand s complexe s nameCoordinati on Number Ag + NH 3 Ag(NH 3 ) 2 + Diamine argentate (I) 2 Cu 2+ NH 3 Cu(NH 3 ) Tetramine cuprate (II) 4 Fe 3+ CN - Fe(CN) 6 3- hexaciano - ferrate (III) 6

The most popular titration  Metal ions + EDTA (Ethylene diamine tetra acetic acid)

REACTION:  Use: EDTA salt (sodium)  easy to solve  Trilon B, Complexone III, atau Titriplex III.

Cu 2+

Simple expression:  Ca 2+ + H 4 Y == CaY H +  Ca 2+ + H 2 Y 2- == CaY H +  Ca 2+ + HY 3- == CaY 2- + H +  Ca 2+ + Y 4- == CaY 2- Always release hydrogen ion  need buffer

indicators:  M + In == Min  MIn + EDTA == M-EDTA + In

Some indicators  Murexide Determination of Ca(II)  pH = 11 Ca + Mur == Ca-Mur red  Ca-Mur + EDTA == Ca-EDTA + Mur red blue-violet

Some Indicators  EBT (Eriochrom Black T): Determination of Mg(II)  pH = 10 Mg + EBT == Mg-EBT red  Ca-EBT + EDTA == Mg-EDTA + EBT red blue

Curve of Titration: 50 mL 0,0100 M Ca 2+ is titrated with 0,0100 M EDTA ( pH 10 )

Application:  Determine water total hardness (Kesadahan total):  Alkali metals : Mg(II) + Ca(II)  Total Hardness: mg of CaCO 3 per liter  Soft water : TD< 60 mg/L