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General Chemistry: Gas Laws and Kinetic Molecular Theory

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  • Kinetic Molecular Theory assumptions
    1. No attractions or repulsions between particles; collisions like billiard ball collisions.
    2. A lot of space between particles compared to their size.
    3. Speed of particles increases with increasing temperature.
  • What causes gas pressure?
    Gas pressure results from constant collisions of gas molecules with surfaces, creating force per unit area.
  • Effect of particle density on gas pressure
    Higher density of gas particles results in higher pressure; lower density results in lower pressure.
  • How does a barometer measure atmospheric pressure?
    A barometer measures pressure by the height of a mercury column balanced by atmospheric pressure.
  • Common pressure units and equivalences
    1 atm = 760 torr = 101,325 Pa = 14.7 psi = 29.92 in Hg = 1 x 10^5 Pa
  • Boyle's Law relationship
    At constant temperature, pressure and volume are inversely proportional: \(P \times V = k\).
  • Molecular explanation of Boyle's Law
    Decreasing volume increases collision frequency of gas molecules with surfaces, increasing pressure.
  • Charles's Law relationship
    At constant pressure, volume is directly proportional to temperature in kelvins: \(\frac{V}{T} = k\).
  • Molecular view of Charles's Law
    Increasing temperature increases particle speed, causing gas volume to expand.
  • Avogadro's Law relationship
    At constant pressure and temperature, volume is directly proportional to number of moles: \(\frac{V}{n} = k\).
  • Combined Gas Law formula
    \(\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}\), relates pressure, volume, and temperature when moles are constant.
  • Ideal Gas Law formula
    \(PV = nRT\), relates pressure, volume, temperature, and moles of gas.
  • Units for Ideal Gas Constant R
    R = 0.08206 L atm / (mol K)
  • Effect of temperature on gas particle speed
    Gas particle speed increases with temperature, increasing kinetic energy.
  • Gas compressibility compared to liquids and solids
    Gases are compressible due to large spaces between particles; liquids and solids are not compressible.
  • Pressure unit Pascal (Pa) definition
    1 Pa = 1 N/m² = 1 kg m⁻¹ s⁻², force per unit area.
  • How does adding mercury in a J-tube affect gas pressure?
    Adding mercury compresses gas, increasing pressure and decreasing volume.
  • Relationship between gas volume and moles
    More gas molecules (moles) at constant P and T means larger volume.
  • How to convert pressure units: psi to mmHg
    Use conversion: psi → atm → mmHg, e.g., 132 psi = 6.82 x 10³ mmHg.
  • What happens to gas volume when temperature increases at constant pressure?
    Gas volume increases as temperature increases, per Charles's Law.