Lecture Notes: Acids and Bases

Introduction

• Importance of Acids and Bases
  • Used in foods, soaps, detergents, fertilizers, explosives, dyes, plastics, pesticides, paper
  • Biological relevance:
    • Stomach acidity, blood is slightly basic
    • Proteins contain amino acids
    • Genetic code (As, Ts, Cs, Gs) involves bases

Historical Perspective

• Ancient Definitions
  • Acids: Sour taste, corrode metal
  • Bases: Slippery feel, counteract acids

Molecular Behavior

• Interaction in Water
  • Exchange of protons (hydrogen ions) and electrons
  • Protons: Positively charged
  • Electrons: Negatively charged
• Molecule Behavior:
  • Donation/acceptance of protons or electrons depending on composition/shape
  • Charge Alteration:
    • Giving up a proton is similar to accepting an electron (more negative)
    • Accepting a proton or donating an electron (more positive)

Strong vs. Weak Acids/Bases

• Strong Acids:
  • Donate protons aggressively, all molecules in sample do so
• Strong Bases:
  • Aggressively accept protons, can rip protons from water
• Weak Acids/Bases:
  • Donate or accept few protons
  • Reach equilibrium; only a small fraction of molecules exchange protons with water
  • Examples:
    • Weak Acid: Vinegar
    • Weak Base: Ammonia

Acid-Base Chemistry in Water

• Water's Dual Role:
  • Acts as acid or base, facilitating deposit and withdrawal of protons
  • Functions like a 24-hour molecular ATM
• Neutralization:
  • Occurs when acid and base interact, canceling out effects on water

Final Note

• Behavior Without Water:
  • Some molecules can behave as acids or bases without water involvement
• Salute to Water:
  • Water as a resilient and fair banker for acids and bases
  • Always open, no interest charges or foreclosure

These notes provide an overview of the roles and behaviors of acids and bases, both historically and at the molecular level, highlighting their significance in both chemistry and biological systems.