Lecture on Water's Properties and Acid-Base Chemistry

Dissociation of Water

• Water can dissociate into ions.
• Dissociation: Breaking apart into hydrogen ions (H+) and hydroxide ions (OH-).

Acid and Base Concepts

• Acids: Solutions where H+ concentration > OH- concentration.
• Bases: Solutions where OH- concentration > H+ concentration.
• Neutral Solutions: Equal concentration of H+ and OH- ions.
• pH Scale: Ranges from 0 to 14.
  • Below pH 7: Acidic
  • Above pH 7: Basic
  • pH 7: Neutral

Reaction of Acids and Bases in Water

• Adding acid to water increases H+ concentration.
• Adding base to water increases OH- concentration.

Buffers and pH Regulation

• Buffers: Maintain stable pH levels in the body.
  • Not always at pH 7; adapt to the normal pH of the specific environment.
  • Example pH levels:
    • Blood: pH 7.3-7.4
    • Stomach: pH 1-2
• Buffer Systems: Adjust pH by shifting reactions.
  • Shift one way if too acidic, another way if too basic.

Chemical Equations Overview

• Chemical Equations:
  • Subscripts indicate the number of atoms.
  • Arrow shows reaction direction: reactants -> products.
  • Conservation of atoms: Same number of each type on both sides.

Reversible Reactions

• Shown with arrows pointing both directions.
• Direction of reaction determines what are reactants and what are products.

Carbonic Acid Buffer System

• Carbonic Acid (H2CO3): Example of a buffer system in the body.
  • Reversible reaction: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
  • Increases acidity when pH is high by releasing H+.
  • Decreases acidity when pH is low by binding H+.

Properties of Water Recap

• High Specific Heat and Heat of Vaporization: Moderates temperature changes.
• Cohesion and Adhesion: Water molecules stick to each other and other surfaces via hydrogen bonds.
• Density: Ice is less dense than liquid water; ice floats.
• Solvent Abilities: Dissolves solutes readily.
• Shape of Molecules: Affects nonpolar molecules' formation; important for cell membranes.

pH Value Questions

• Strongest acid: pH 1.0
• Strongest base: pH 14.0
• Neutral: pH 7

Buffer Functionality

• Buffers do not target pH 7 universally; they maintain normal pH for specific environments.
• Adjust by releasing or tying up hydrogen ions.

Next Topic: Introduction to Organic Chemistry.