Titasi Kompleksometri Complexometric Titrationtitrasi kompleksometri络合滴定法.pptVIP

* * * * * * * * * * * * * * * * * * * * * * Teknologi dan Rekayasa Complexometric Titration SMK Negeri 13 Bandung Complexometric Titration Reaction result is complex substance Common standard solution : EDTA (Ethylene Diamine Tetra acetic Acid ) What is complex substance? A substance formed by covalent coordination bond; A bonding formed by pair electrons sharing, while the source of pair electrons is only one atom/group. The covalent coordinate in a complex substance Between the center atom (metal ion) and the ligand (ion/atom/group that give the pair electrons). Center atom give the orbital. Ligand give the pair electrons. Complex stability If Mn+ + Lx- ? [ML]n-x While [ML]n-x is complex substance then [ML] K = ----------- is Kstab [M] [L] Kstab= stability constant The more stable the substance will has bigger Kstab The complex is difficult to dissociated to be its ions (Compare with weak acid or base) EDTA(Ethylene Diamine Tetra acetic Acid) Ligand that have 6 pairs of electron. Other name : trilon B, complexon III, sequestrene, versene dan chelaton 3. Release 2 H+ from 2 carboxylic. Most available in disodium salt form. Wrote as H2Y= EDTA concentration always termed in Molar, because EDTA has 6 electrons pair which could be used in covalent coordinate bond one-by-one. EDTA reacts with any metal with mole ratio 1 : 1. REACTIONS M2+ + H2Y= ? MY= + 2H+ M3+ + H2Y= ? MY- + 2H+ M4+ + H2Y= ? MY + 2H+ M5+ + H2Y= ? MY+ + 2H+ Mn+ + H2Y= ? MY(n-4) + 2H+ pH influence to metal-EDTA complex stability Every reaction of metal ion with EDTA resulted H+ As Le Chatelier, if [H+] increased, the equilibrium goes to the left (ions) means At low pH or high [H+] , the stability of metal-EDTA is decreased. Some of Kstab of metal-EDTA 2+ Ions 3+ Ions Mg 8.7 Al 16.3 Ca 10.7 Fe 25.1 Sr 8.6 Y 18.2 Ba 7.8 Cr 24.0 Mn 13.8 Ce 15.9 Fe 14.3 La 15.7 Co 16.3 Lu 20.0 Ni 18.6 Se 23.1 The Equivalence