Gas Laws: MCQ 4
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Questions and Answers

What is the value of the universal gas constant R?

  • 10.31 K.K⁻¹.mol⁻¹
  • 8.31 K.K⁻¹.mol⁻¹ (correct)
  • 7.31 K.K⁻¹.mol⁻¹
  • 9.31 K.K⁻¹.mol⁻¹

    • What is the unit of pressure in the equation of state for an ideal gas?

  • Pa (correct)
  • atm
  • mPa
  • kPa

    • What is the formula to calculate the number of moles of a gas?

  • moles = mass * Mr
  • moles = mass / R
  • moles = mass * R
  • moles = mass / Mr (correct)

    • What is the purpose of the pinhole in the aluminum foil in the experiment to find the Mr of a volatile liquid?

    <p>To equalise the pressure inside the flask with atmospheric pressure outside</p> Signup and view all the answers

    What is the unit of volume in the equation of state for an ideal gas?

    <p>m³</p> Signup and view all the answers

    What is the formula to calculate the volume of an ideal gas?

    <p>V = nRT / P</p> Signup and view all the answers

    What is the unit of temperature in the equation of state for an ideal gas?

    <p>K</p> Signup and view all the answers

    What is the purpose of the thermometer in the experiment to find the Mr of a volatile liquid?

    <p>To measure the temperature of the vapour</p> Signup and view all the answers

    What is the main assumption of the kinetic theory of gases that real gases do not fully obey?

    <p>The particles have negligible volumes compared to the distances between them</p> Signup and view all the answers

    What is the result of particles being closer together at low temperature and high pressure?

    <p>Their volumes are no longer negligible compared to the distances between them</p> Signup and view all the answers

    What type of forces cause the greatest deviation from ideal gas behavior?

    <p>Attractive forces such as Van Der Waals', dipole-dipole, and hydrogen bonding</p> Signup and view all the answers

    Under what conditions do real gases behave most like ideal gases?

    <p>At high temperatures and low pressures</p> Signup and view all the answers

    What is the characteristic of an ideal gas?

    <p>It is an imaginary gas that obeys all the assumptions of the kinetic theory under all conditions</p> Signup and view all the answers

    Why do real gases deviate from the kinetic theory of gases?

    <p>Because their particles are attracted or repelled from one another</p> Signup and view all the answers

    What is the result of the average kinetic energy of the particles being proportional to the Kelvin temperature?

    <p>The particles move faster</p> Signup and view all the answers

    Study Notes

    Kinetic Theory of Gases

    • The kinetic theory is based on 5 assumptions:
      • Gases are made up of particles with negligible volumes compared to distances between them
      • No attractive or repulsive forces between gases
      • Particles are in constant rapid random motion, colliding with each other and the container walls
      • Average kinetic energy of particles is proportional to the Kelvin temperature
      • All collisions are perfectly elastic

    Real Gases and Ideal Gases

    • Real gases (e.g., O₂, N₂, Cl₂, CO₂) do not fully obey the kinetic theory assumptions
    • Ideal gases obey all the assumptions of the kinetic theory under all conditions of temperature and pressure
    • Real gases deviate most from the kinetic theory at low temperatures and high pressures

    Behaviour of Real Gases

    • At low temperatures and high pressures, particles become closer together, and their volumes are no longer negligible
    • Attractive forces between particles cause deviations from ideal gas behaviour
    • Real gases behave most like ideal gases at high temperatures and low pressures

    Equation of State for an Ideal Gas

    • PV = nRT, derived from a combination of Boyle's, Charles', and Avogadro's Laws
    • n = number of moles
    • R = universal gas constant (8.31 K.K⁻¹.mol⁻¹)
    • Units: Volume (m³), Pressure (Pa), Temperature (K)

    Calculations

    • Example 1: Calculating the volume occupied by 10g of oxygen gas at 25°C and 200kPa
    • Example 2: Calculating the Mr of a volatile liquid from the volume of vapour measured at 100°C and 100kPa

    Experiment to Find the Mr of a Volatile Liquid

    • A volatile liquid is one that vaporises easily (low boiling point)
    • The most accurate method is using a mass spectrometer, but a simpler method can be used in the school lab
    • The experiment involves measuring the mass of the condensed liquid, volume of the flask, atmospheric pressure, and temperature of the vapour
    • The measurements are then used to calculate the number of moles and Mr of the volatile liquid

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    Description

    This quiz covers the assumptions and principles of the kinetic theory of gases, including the behavior of ideal and real gases.

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