Ionic Equilibrium Lecture

Introduction

• Important Unit: Ionic equilibrium is an important topic in chemistry, especially in physical chemistry.
• Difficulty: Students feel anxious due to the calculative part.
• Key Topics: Salt Hydrolysis, Arrhenius Theory, Acid-Base Combinations.

Bronsted-Lowry Concept

• Acid: Donates H⁺ (proton).
• Base: Accepts H⁺.
• Conjugate Acid-Base Pair: What is formed after an acid loses its H⁺ is its conjugate base and vice-versa.

Conjugate Acid-Base Pair

• Definition: Species formed after removal/addition of H⁺ from base/acid.
• Example: HCl → Cl⁻ (conjugate base).

Amphiprotic Species

• Definition: Species that can donate and accept protons.
• Example: HSO₄⁻, H₂PO₄⁻.

Leveling Effect of Water

• All strong acids and bases show equal strengths in water.

Electrolytes

• Strong Electrolytes: 100% ionized.
• Weak Electrolytes: Partially ionized.

Arrhenius Theory of Electrolyte Dissociation

• Discussion on the ionization constant of a weak electrolyte.

Properties of Water

• Weak Electrolyte: Water undergoes auto-ionization.
• Ionic Product: KW = [H⁺][OH⁻] = 10⁻¹⁴

pH Scale

• Neutral Water: pH = 7
• PH Calculation: pH = -log[H⁺]

Common Ion Effect

• The dissociation of a weak electrolyte decreases when a strong electrolyte with a common ion is added to it.

Calculation of pH

• Strong Acid/Base: pH is directly derived from the concentration.
• Mixture of Strong Acids/Bases: Mainly determined by the neutralization reaction.

pH of Weak Acid/Base

• Concentration of H⁺ is derived from the dissociation constant.

Note: To complete the whole chapter, it is necessary to see the next part.