Chemistry: The Central Science - Chapter 10 Summary

Characteristics of Gases

  • Similar physical properties
  • Mainly nonmetallic elements with low molar masses
  • Properties: expand to fill containers, highly compressible, low densities
  • Form homogeneous mixtures

Common Gases

  • Examples include:
    • HCN: Toxic, bitter almond smell
    • H2S: Toxic, rotten egg smell
    • CO: Colorless, odorless
    • CO2: Colorless, odorless
    • CH4: Colorless, odorless, flammable

Pressure

  • Defined as force per unit area
  • Atmospheric pressure: weight of air per unit area

Units of Pressure

  • Pascal (Pa), Bar (1 bar = 100 kPa), mm Hg or torr
  • 1 atm = 760 torr = 760 mm Hg = 101.325 kPa

Manometer

  • Measures gas pressure relative to atmospheric pressure

Ideal Gas Laws

  1. Boyle’s Law: PV = constant (inversely proportional)
  2. Charles’s Law: V ∝ T (directly proportional)
  3. Avogadro's Law: V ∝ n (directly proportional)
  4. Ideal Gas Equation: PV = nRT

Gas Density and Molar Mass

  • Density formula: d = \frac{PM}{RT}

Kinetic-Molecular Theory

  • Gases consist of many molecules in random motion
  • Negligible volume and influences between gas molecules
  • Average kinetic energy is proportional to temperature

Effusion and Diffusion

  • Effusion: escape through tiny holes
  • Diffusion: spread of one substance through another
  • Graham’s Law: Lighter gases effuse faster than heavier gases

Real Gases

  • Deviate from ideal behavior at high pressures and low temperatures
  • Van der Waals Equation: Corrects ideal gas law for real gas behavior by adjusting pressure and volume due to intermolecular forces and finite volume.