chapter 10: gases

• According to the kinetic molecular theory, a gas is a collection of particles (either molecules or atoms, depending on the gas) in constant motion
• The three postulates of the kinetic molecular theory are:

  • The size of the particle is negligibly small
  • Average kinetic energy is proportional to the temperature (in K)
  • Collisions between particles or a wall is completely elastic
• The total kinetic energy is preserved before and after an elastic collision.
• Pressure is a result of the sum of the forces of gas particles colliding with one another and on surfaces.
• Pressure = force of the collisions / area of the surface
• Pascal = 1 N / m^2
• 1 Atm = 760 mm Hg
• 1 Torr = 1 mm Hg
• 1 atm = 1.01325 bar
• A barometer measures atmospheric pressure.
• A manometer is used in the lab to measure the pressure of a sample of gas.
• Boyle's Law says that the volume of a gas is inversely proportional to pressure (temperature is constant)
• Charle's Law says that the volume of a gas is proportional to the temperature (pressure is constant)
• Avogadro's Law says that the volume of a gas is proportional to the number of moles of gas present
• The ideal gas law is represented by PV = nRT

  P - atm

  V - liters

  T - Kelvins

  n - mol

  R is the ideal gas constant, equal to 0.08206 (L)(atm) / (mol)(K)
• moles = mass of substance (g) / molar mass of substance (g/mol)