Chapter 1: Basic Concepts of Chemistry

Introduction

• Importance of Chemistry: Understanding the significance of chemistry in everyday life.
• Basic Concepts Covered:
  • Chemicals and their uses
  • Significant figures
  • Elements and mixtures
  • Chemical combinations
  • Laws of Chemical Combination

Laws of Chemical Combination

• Importance: These laws determine how elements combine to form compounds.
• Number of Laws: There are 5 main laws governing chemical combinations.

Law 1: Law of Conservation of Mass

• Definition: Mass is neither created nor destroyed in a chemical reaction. The sum of the masses of the reactants equals the sum of the masses of the products.
• Historical Context: Discovered between the 1740s and 1780s; no new laws have been added since.
• Concept Example:
  • Reaction: Carbon (C) combines with Oxygen (O2) to form Carbon Dioxide (CO2).
  • Mass Calculation:
    • Atomic mass of Carbon (C): 12
    • Atomic mass of Oxygen (O): 16
    • For CO2: 12 (C) + 2×16 (O) = 44
    • The mass of reactants (12 + 32) equals the mass of the products (44).
• Modern Context: The basic law still applies, although modern understanding includes energy-mass conversion (E=MC^2) which was not considered at the time.

Example Problem

• Given:
  • 1.5 grams of Ethane (C2H6)
  • Results: 44 grams of CO2 and 2.7 grams of H2O
• Task: Prove that this reaction obeys the law of conservation of mass by writing out and balancing the chemical equation.