Transcript Ch. 3. KINETIC VS. EQUILIBRIUM MODELING

Ch. 4. AQUEOUS COMPLEXES
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4-1. A Few Definitions
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Aqueous complexes
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Ligands
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Ions or molecules binding to a central metal to form a complex (by
donating electron pair)
Addend
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Association of dissolved (c,a)ions or molecules
Pieces of complexes (either cations or anions)
Monodendate (Cl-), bidendate (CO32-), polydendate
Chelates
P. 91, Table 3.2
Description: Chemical structure of EDTA chelate
(from wikipedia.org)
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4-2. Significance of Complexes
Speciation of metals
 Adsorption
 Toxicity
 Solubility
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4-3. Outer vs. Inner Sphere Complexes
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Hydration (shell)
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Outer sphere complex (ion pair): ex) CaSO4
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Inner sphere coplex: ex) AgS
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Weak, electrostatic (depending on charges)
Strong, covalency
Most complexes are in between
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4-4. Geometry of Common Inorganic Ligands
All depends on the radius ratio (p.89)
 Plan triangular triangle (NO3-, CO3-, BO3-)
 Regular trigonal low pyramidal (PO33-, AsO33- )
 Regular tetrahedron (PO43-, SO42-, CrO43- )
 Distorted tetrahedron (MoO42-)
 Spherical (halogens)
 Dumbel shape (UO22- )
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See page 89 & 90 tables
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4-5. Complexation Mass Balance & Equilibria
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Extent of complex formation (average ligand
number)
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Stepwise formation constant
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P. 90, eqn (3.17)
P. 92, eqn (3.18)
Cumulative formation constant
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P.92, eqn (3.21)
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4-6. Hydrolysis of Cations in Water and Ionic
Potential
Hydrolysis?
 Ionic potential?
 How these two factors affect the behavior of the
dissolved ions in water?
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See p.98, Fig. 3.4; p.99, Table 3.3.; p.100, Fig. 3.5
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4-7. Electronegativities & the Stability of
Inner-Sphere Complexes
What is EN? (p.101, Tanle 3.4)
 How does EN controls bonding character ?
 Conseq., the stabilities of complexes? (p.102, Fig.
3.6)
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4-8. Schwarzenbach’s & Pearson’s Classification of
Acids & Bases (forming Complexes)
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Schwarzenbach’s classes A, B, & C
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Pearson’s hard & soft
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A: Those of noble gas configuration (p.103, bottom table)
B: Those of Nio, Pdo, Pto electron config.
C: Transient metals
Hard: Rigid & nondeformable elctron cloud, tend to form ionic
bonding
Soft: Deformable & polarizable electron cloud, tend to form (more)
covalent bonding
See p.104, Table 3.5; p.105, Fig. 3.7; p.106, Fig. 3.8; p.108,
Fig. 3.9.
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4-9. Thermodynamics of Complexation
DGo = -RT ln Kassoc
 DGo = DGo - TDSo
 Mostly due to entropy change
 DSo = DSonet charge + DSotr + DSorot + DSovibr +
DSodehyd
 DSodehyd is probably contributing most
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4-10. Distribution of Complex Species as a
Function of pH
Write down the association reactions
 Express Kassoc in terms of species
 Convert them into a function of pH
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See p.113, Fig. 3.12