Summary of "2 Solubility Ksp"

Summary of "2 Solubility Ksp" Video

This video explains the concept of solubility product constants (Ksp) for slightly soluble (insoluble) ionic compounds and how to write their dissociation reactions and equilibrium expressions.

Main Ideas and Concepts:

Insoluble Compounds Have Slight Solubility:
- Even compounds considered insoluble dissolve slightly, establishing an equilibrium between the solid and its ions in solution.
- Example: Lead(II) chloride (PbCl₂) is insoluble but dissociates slightly into Pb²⁺ and Cl⁻ ions.
Writing Dissociation Reactions:
- When writing dissociation, break the compound into its constituent ions.
- Pay attention to stoichiometry (number of ions produced).
- Polyatomic ions do not break apart further (e.g., carbonate CO₃²⁻ remains intact).
Writing Ksp Expressions:
- Ksp is the equilibrium constant for the dissolution of an ionic solid.
- It is the product of the concentrations of the ions, each raised to the power of their stoichiometric coefficients.
- Solids are not included in the equilibrium expression.
- The expression is a product, not a sum (no plus signs between ion concentrations).
Examples of Dissociation and Ksp Expressions:
- PbCl₂: PbCl₂ (s) ⇌ Pb²⁺ (aq) + 2Cl⁻ (aq) Ksp = [Pb²⁺][Cl⁻]²
- CaF₂: CaF₂ (s) ⇌ Ca²⁺ (aq) + 2F⁻ (aq) Ksp = [Ca²⁺][F⁻]²
- Ag₂CO₃: Ag₂CO₃ (s) ⇌ 2Ag⁺ (aq) + CO₃²⁻ (aq) Ksp = [Ag⁺]²[CO₃²⁻]
- Ca₃(PO₄)₂: Ca₃(PO₄)₂ (s) ⇌ 3Ca²⁺ (aq) + 2PO₄³⁻ (aq) Ksp = [Ca²⁺]³[PO₄³⁻]²
Interpreting Ksp Values:
- Ksp values are typically very small, reflecting the low solubility of these solids.
- Larger Ksp means higher solubility; smaller Ksp means lower solubility.
- Example Ksp values:
  - CaF₂ = 4 × 10⁻¹¹
  - Ag₂CO₃ = 8.1 × 10⁻¹²
  - Ca₃(PO₄)₂ = 1.3 × 10⁻³² (least soluble among these)

Methodology / Instructions:

Identify the ionic compound and write its dissociation reaction into ions.
Note the stoichiometric coefficients for each ion.
Write the Ksp expression as the product of the ion concentrations, each raised to the power of their stoichiometric coefficient.
Remember to exclude solids from the equilibrium expression.
Use tables of Ksp values to compare solubilities.
Interpret the magnitude of Ksp to understand relative solubility.