Lecture Notes: Understanding Acids and Bases

Introduction

• Common terms: acid and base
• Focus: Molecular understanding of acids and bases

Bronsted-Lowry Model

• Acid: Donates a hydrogen ion (H+)
• Base: Accepts a hydrogen ion
• Acid-base reaction: Transfer of a hydrogen ion from one molecule to another

Hydrogen Ion

• H+ ion: Referred to as a proton
• A hydrogen atom (1 proton, 1 electron) becomes H+ by losing its electron

Dissociation of Strong Acids

• In aqueous solution, every acid molecule transfers a proton to water
• Forms hydronium ion (H3O+)

Example: Hydrochloric Acid

• Reaction: HCl + H2O → Cl- (conjugate base) + H3O+ (conjugate acid)
• Each acid molecule transfers a proton to a water molecule

Types of Acids

• Strong Acids: Fully dissociate in solution
• Weak Acids: Partially dissociate, establishing an equilibrium with their conjugate base

Bases

• Strong Base: Steals a proton from water, producing hydroxide ion (OH-)
• Some strong bases contain hydroxide ions
• Weak Bases: Partially react in solution

Amphoteric Nature of Water

• Water (H2O): Can act as both an acid and a base
  • As a base: Reacts with acid to form hydronium
  • As an acid: Reacts with base to form hydroxide

Neutralization Reaction

• Occurs when a strong acid and base react
• Products: Water molecules (neutral compound)
• Remaining ions: Stay in solution

Predicting Reaction Products

• Example: Hypochlorous acid (acid) and water (base)
  • Products: Hypochlorite ion (conjugate base) and hydronium (conjugate acid)

Conclusion

• Understanding molecular interactions in acid-base reactions
• Identification of acids and bases using Bronsted-Lowry model