Unit 6 Equilibrium

Importance of Chemical Equilibria

• Critical in biological processes (e.g., oxygen and carbon monoxide with hemoglobin)
• Environmental processes (e.g., evaporation and condensation)
• Dynamic nature of equilibria at molecular boundary

Understanding Equilibrium

• Equilibrium: rate of evaporation = rate of condensation
• Physical and chemical equilibria
• Dynamic equilibrium: no net concentration change
• Three types of reactions:
  1. Nearly complete reactions
  2. Minimal product formation
  3. Comparable reactant and product concentrations

Factors Affecting Equilibrium

• Concentrations, temperature, etc.
• Optimization important in industrial processes

Equilibrium in Physical Processes

Solid-Liquid Equilibrium

• Ice and water equilibrium at 273K
• Mass and temperature constancy

Liquid-Vapour Equilibrium

• Vapour pressure constancy
• Different liquids have different vapour pressures

Solid-Vapour Equilibrium

• Sublimation: e.g., iodine, camphor, NH4Cl

Dissolution Equilibria

• Solids in liquids: saturation and dynamic equilibrium
• Gases in liquids: Henry's Law, pressure relation

General Characteristics of Equilibria

• Closed system requirement
• Dynamic stability and constancy of measurable properties

Equilibrium in Chemical Processes

• Dynamic equilibrium in reversible reactions
• Concentration constancy at equilibrium

Law of Chemical Equilibrium and Equilibrium Constant

• Equilibrium constant (Kc) relationships
• Kc expressed using concentration ratios
• Kp for gases, relationship with Kc

Homogeneous and Heterogeneous Equilibria

• Homogeneous: same phase
• Heterogeneous: different phases, simplification with pure solids/liquids

Predicting Reaction Extent and Direction

• Magnitude of Kc indicates reaction completeness
• Reaction quotient (Qc) predicts direction

Le Chatelier’s Principle

• System counteracts changes to restore equilibrium
• Effects of concentration, pressure, temperature, and catalysts

Ionic Equilibrium in Solutions

• Electrolytes and ionization
• Arrhenius, Brønsted-Lowry, and Lewis definitions
• Ionization constants (Ka and Kb), pH scale

Acids, Bases, and Salts

• Examples of acids and bases from daily life
• Strong vs. weak electrolytes

Ionization of Acids and Bases

• Arrhenius and Brønsted-Lowry concepts
• Conjugate acid-base pairs

Ionization Constants

• Calculating pH, degree of ionization
• Effect of common ions

Buffer Solutions

• Resist pH changes
• Designed using Henderson-Hasselbalch equation

Solubility Equilibria

• Sparingly soluble salts
• Solubility product constant (Ksp)
• Common ion effect on solubility

Summary

• Dynamic nature of equilibrium
• Application of equilibrium principles in various processes

These notes provide a structured overview of the key concepts from Unit 6 on Equilibrium, covering both physical and chemical processes, factors affecting equilibrium, and applications in real-world situations.