Chapter 19. Solubility and Complex Ion Equilibria
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1. Solubility
2. Solubility Product Constant
a. Toothpaste and Solubility Product Constant
1. Solubility
⑴ Solubility of Solids : Solubility increases as temperature increases
① ΔG = ΔH - TΔS
② ΔH lattice ≒ ΔH hydration ⇒ ΔH solution ≃ 0
③ Dissolution of solids is a reaction with ΔS ＞ 0
④ T↑ ⇒ ΔG↓
⑵ Solubility of Liquids : Solubility increases as temperature increases
① ΔG = ΔH - TΔS
② ΔH lattice ≒ ΔH hydration ⇒ ΔH solution ≃ 0
③ Dissolution of liquids is a reaction with ΔS ＞ 0
④ T↑ ⇒ ΔG↓
⑶ Solubility of Gases : Solubility decreases as temperature increases
① ΔG = ΔH - TΔS
② ΔH lattice ≒ ΔH hydration ⇒ ΔH solution ≃ 0
③ Dissolution of gases is a reaction with ΔS ＜ 0
④ T↑ ⇒ ΔG↑
⑷ Limiting Enthalpy of Solution
① Definition : Enthalpy of formation of a dilute solution where solute-solute interactions can be neglected
2. Solubility Product Constant
⑴ Solubility Product Constant
① Definition : Taking AgCl as an example.
○ Definition of Precipitation : When [Ag+] × [Cl-] < Ksp, the degree of freedom of AgCl( s ) is not 1, so it is defined as not precipitating.
○ Precipitation reaction is a specific form of acid-base reaction.
② Relationship with Solubility s (g/L)
③ Solubility Product Constant Ksp at 25 ℃
Table. 1. Solubility Product Constants at 25 ℃
④ Major Precipitates
○ Calcium Carbonate (CaCl2) : White precipitate
○ Barium Sulfate (BaSO4) : White precipitate
○ Lead Iodide (PbI2) : Yellow precipitate
○ Silver Chloride (AgCl) : White precipitate
○ Silver Iodide (AgI) : Yellow precipitate
○ Manganese Dioxide (MnO2) : Brown precipitate
○ Fe(OH)2 : Green rust
○ Fe(OH)3 : Dark orange
⑵ Precipitation : The phenomenon of forming solid products and settling due to excessive presence of ions.
① Precipitation : Comparing Reaction Quotient Q with Ksp
○ Q > K : Precipitation occurs ↔ Excess ions present
○ Q < K : No precipitation reaction occurs ↔ Insufficient ions present
② Common Ion Effect : Decrease in solubility in the presence of a common ion.
③ Salt Effect
⑶ Common Ion Effect
⑷ pH and Solubility
① Hydroxides
② Basic Salts
3. Complex Ion Equilibria
⑴ Formation Constant Kf
⑵ Formation and Solubility of Complexes
⑶ Amphiprotic Elements
Input: 2018.12.27 14:54