Chemistry Chapter 5: Gases
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Questions and Answers

What happens to the average speed of gas molecules as temperature increases?

  • It increases due to higher kinetic energy. (correct)
  • It becomes unpredictable and erratic.
  • It remains constant regardless of temperature.
  • It decreases due to reduced energy.
  • Which gas will have the lowest average speed at a fixed temperature?

  • C3H8 (correct)
  • CO2
  • N2
  • O2
  • In the van der Waals equation, what does the term 'a' correct for?

  • Behavioral changes under extremely low temperatures.
  • Attractive forces between particles at low temperatures. (correct)
  • Volume occupied by gas particles at high pressures.
  • Energy losses due to collisions.
  • Which gas is likely to resemble an ideal gas at lower temperatures?

    <p>He (A)</p> Signup and view all the answers

    Which gas has the highest average kinetic energy at STP?

    <p>They all have the same average kinetic energy. (D)</p> Signup and view all the answers

    What is the total pressure when carbon dioxide (PCO2) and water vapor (PH2O) are combined, given PT = (PCO2 + PH2O)?

    <p>21 atm (B)</p> Signup and view all the answers

    According to the ideal gas law, which of the following variables is directly proportional to the number of moles of a gas, assuming temperature and volume are constant?

    <p>Pressure (D)</p> Signup and view all the answers

    What must be calculated first in order to find the volume of oxygen needed for the reaction involving 620 kg of ZnS?

    <p>Number of moles of ZnS (D)</p> Signup and view all the answers

    What is the relationship between the average kinetic energy of a gas and its absolute temperature according to Kinetic Molecular Theory?

    <p>They are directly proportional (B)</p> Signup and view all the answers

    Which of the following is a postulate of Kinetic Molecular Theory?

    <p>Gas particles are in constant, random motion. (C)</p> Signup and view all the answers

    What is the approximate pressure of water vapor in a flask if 0.050 g of B4H10 burns completely, producing gaseous water in a 4.25-L container at 30.0 °C?

    <p>1.2 atm (D)</p> Signup and view all the answers

    Which of the following statements accurately describes non-ideal gas behavior?

    <p>Gas particles occupy significant volume at high pressure. (D)</p> Signup and view all the answers

    To solve for the mass of KClO3 used in the reaction that produces 386 mL of oxygen, which calculation is necessary first?

    <p>Determine moles of oxygen produced. (D)</p> Signup and view all the answers

    Which equation represents the ideal gas law?

    <p>PV = nRT (D)</p> Signup and view all the answers

    What is the function of the universal gas constant R in the ideal gas law?

    <p>To ensure unit consistency in the equation (D)</p> Signup and view all the answers

    Which gas law describes the direct relationship between volume and temperature?

    <p>Charles’s Law (B)</p> Signup and view all the answers

    What happens to the pressure of a gas when its volume is decreased while keeping temperature constant?

    <p>The pressure increases (A)</p> Signup and view all the answers

    Which of the following is a postulate of the kinetic theory of gases?

    <p>Gas molecules occupy a negligible volume compared to the container. (B)</p> Signup and view all the answers

    What is the initial pressure of a gas if its volume changes from 39 mL to 514 mL and the final pressure is 720 torr?

    <p>553.4 torr (C)</p> Signup and view all the answers

    In a mixture of gases, what term defines how each gas contributes to the total pressure?

    <p>Partial pressure (C)</p> Signup and view all the answers

    How does the density of gases generally compare to that of solids and liquids?

    <p>Gases typically have much lower densities than solids or liquids. (C)</p> Signup and view all the answers

    How many moles of an ideal gas are present when the gas occupies a volume of 158 L at 14°C and a pressure of 89 kPa?

    <p>4.32 moles (D)</p> Signup and view all the answers

    What is the total pressure in a flask containing H2O and O2 if the partial pressures are 0.42 atm for H2O and 0.21 atm for O2?

    <p>0.63 atm (D)</p> Signup and view all the answers

    If a gas behaves ideally, what is the relationship between temperature, volume, and pressure described by the ideal gas law?

    <p>PV = nRT (B)</p> Signup and view all the answers

    At standard temperature and pressure (STP), which of the following gases will occupy the greatest volume when given 2.0 g of each?

    <p>CH4 (D)</p> Signup and view all the answers

    Which law states that the total pressure of a gas mixture is equal to the sum of the partial pressures of its components?

    <p>Dalton's Law (A)</p> Signup and view all the answers

    How is the mole fraction of a gas in a mixture calculated?

    <p>Xi = ni / ntotal (D)</p> Signup and view all the answers

    For a gas sample containing 259 moles of CO2 and 513 moles of water, what is the partial pressure of CO2 if the total pressure is 21 atm?

    <p>2.05 atm (D)</p> Signup and view all the answers

    What is the standard molar volume of an ideal gas at standard temperature and pressure (STP)?

    <p>22.4 L (C)</p> Signup and view all the answers

    Flashcards

    Ideal Gas Law

    The equation PV = nRT describes the relationship between pressure (P), volume (V), number of moles (n), and temperature (T) of an ideal gas.

    Gas Pressure

    Gas pressure is the force exerted by gas molecules colliding with the walls of a container.

    Charles's Law

    The volume of a gas is directly proportional to its absolute temperature at constant pressure.

    Boyle's Law

    The volume of a gas is inversely proportional to its pressure at constant temperature.

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    Avogadro's Law

    The volume of a gas is directly proportional to the number of moles of gas at constant temperature and pressure.

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    Absolute Temperature

    Temperature measured in Kelvin (K). It's zero when there's no kinetic energy in the molecules.

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    Partial Pressure

    The pressure exerted by a single gas in a mixture of gases.

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    Kinetic Theory of Gases (KMT)

    A model explaining gas behavior based on the motion of gas particles.

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    Mole Fraction (Xi)

    The ratio of the moles of a particular gas component (ni) to the total moles of gas in the mixture (ntotal).

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    Dalton's Law of Partial Pressures

    The total pressure of a gas mixture is the sum of the partial pressures of each component gas.

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    STP (Standard Temperature and Pressure)

    Standard conditions for gases, defined as 0°C (273.15 K) and 1 atm pressure.

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    Molar Gas Volume

    The volume occupied by one mole of any ideal gas at STP.

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    Volume of gases at constant T & P

    Equal volumes of gases at the same temperature and pressure contain the same number of moles or molecules.

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    Partial pressure equation

    The partial pressure of a gas, Pi, is related to its mole fraction and total pressure by the equation Pi = Xi * Ptotal.

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    Ideal Gas Law Equation

    The ideal gas law relates pressure (P), volume (V), moles of gas (n), ideal gas constant (R), and absolute temperature (T) for an ideal gas. PV = nRT

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    Stoichiometry of Gas Reactions

    In chemical reactions involving gases, use the ideal gas law (PV=nRT) to determine the amount of gas involved in a reaction.

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    Nonideal Gas Behavior

    Gases don't always behave ideally, especially at high pressures or low temperatures. Real gas behavior deviates from the ideal gas law predictions.

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    Kinetic Molecular Theory (KMT)

    A model explaining the behavior of gases. It connects macroscopic gas properties to microscopic gas particle behavior.

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    Elastic Collisions in KMT

    Collisions between gas molecules and container walls conserve kinetic energy; no energy loss during collisions.

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    Average Kinetic Energy (KE) of a Gas

    The average kinetic energy of a gas is proportional to its absolute temperature.

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    Gas particle interactions in KMT

    Gas particles in KMT mostly don't affect each other except during collisions.

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    Molar Volume of a Gas

    Molar volume is the volume occupied by 1 mole of a gas at standard temperature and pressure (STP).

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    What does KEavg represent?

    KEavg stands for the average kinetic energy of gas molecules. It's the measure of their average translational motion.

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    How does temperature affect KEavg?

    As temperature increases, the average kinetic energy (KEavg) of gas molecules also increases. This is because hotter molecules move faster and have more energy.

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    What is the relationship between KEavg and temperature?

    The average kinetic energy (KEavg) of an ideal gas is directly proportional to its absolute temperature. This means that if you double the temperature, you double the average kinetic energy.

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    What is the van der Waals equation?

    The van der Waals equation is a modified version of the ideal gas law that accounts for the real-world behavior of gases, specifically their intermolecular forces and volume.

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    What does the 'a' term in the van der Waals equation account for?

    The 'a' term in the van der Waals equation corrects for the attractive forces between gas molecules. These forces are stronger at lower temperatures.

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    Study Notes

    Chapter 5: Gases

    • Gases expand to fill any container they are placed in.
    • Gases mix readily and thoroughly with each other.
    • Gas volume changes greatly with varying temperatures.
    • Gases have variable densities dependent on conditions.
    • Gases have much lower densities than solids or liquids.

    Chapter 5 Objectives

    • Use the ideal gas law to calculate changes in gas conditions.
    • Apply the concept of partial pressure to analyze gas mixtures.
    • Calculate stoichiometric values for reactions involving gases.
    • State the postulates of the kinetic theory of gases (KMT).
    • Explain how the kinetic theory explains the behavior of gases.
    • Distinguish between ideal and real gases.

    Properties of Gases

    • Gas pressure results from molecular collisions between gas molecules and container walls.
    • Each collision imparts a small amount of force.
    • The total force of these collisions produces macroscopic pressure.
    • Pressure is measured using a barometer, where the height of the mercury column is proportional to atmospheric pressure.
    • 1 torr = 1 mm Hg, 1 atm = 760 torr.

    The Ideal Gas Law

    • PV = nRT, where:
      • P = pressure
      • V = volume
      • n = moles of gas
      • R = ideal gas constant (0.08206 L atm mol⁻¹ K⁻¹)
      • T = absolute temperature (in Kelvin)
    • Moles = mass/molar mass

    The Gas Laws

    • Charles's Law: V ∝ T
    • Boyle's Law: V ∝ 1/P
    • Avogadro's Law: V ∝ n
    • The ideal gas law combines these empirical gas laws.

    Charles's Law

    • Jacques Charles studied the relationship between volume (V) and temperature (T)
    • Plots of V vs T for different gases converge to the same temperature at zero volume (absolute zero ≈-273°C).

    Example Problems (Illustrative, not exhaustive)

    • Problem solving examples provided on pages 9, 10, 11, 12, 19, 21, 22, 23. This involves applications of the gas laws, like Boyle’s law, Charles’ law and the ideal gas law.

    Kinetic Molecular Theory (KMT)

    • Gases are composed of tiny particles in constant, random motion.
    • Gas particles have negligible volume compared to the container volume.
    • Collisions between gas particles and container walls are elastic (no energy loss).
    • Gas particles exert no significant attractive or repulsive forces on each other except during collisions.
    • The average kinetic energy of gas particles is proportional to the absolute temperature.

    Postulates of the Model

    • Gases consist of large collections of particles moving randomly.
    • Gas particles are very small and occupy negligible volume.
    • Gas collisions with the container walls are elastic, conserving kinetic energy.
    • Gas particles interact with each other only during collisions.
    • Average kinetic energy is proportional to temperature, regardless of particle identity.
    • As temperature rises, average speed increases.
    • At a given temperature, heavier particles move slower on average than lighter particles.

    Limitations of KMT

    • At high pressure, particle volume becomes significant.
    • At low temperatures, intermolecular forces become important.

    Correcting the Ideal Gas Equation

    • The van der Waals equation accounts for particle volume and intermolecular forces:
      • (P+an2V2)(V−nb)=nRT(P + \frac{an^2}{V^2})(V - nb) = nRT(P+V2an2​)(V−nb)=nRT
      • a corrects for intermolecular attractions
      • b corrects for particle volume

    Partial Pressure

    • Dalton's Law of Partial Pressures: The total pressure of a mixture of gases is the sum of the partial pressures of the individual gases.
    • Partial pressure depends on the mole fraction of each gas.
    • Mole fraction (Xᵢ) = (moles of gas i) / (total moles of gas).

    Stoichiometry of Reactions Involving Gases

    • Ideal gas law (PV=nRT) is often used to solve gas stoichiometry problems by relating moles of gas to pressure, volume, or temperature.

    Additional Notes

    • Real gases deviate from ideal gas behavior under high pressure and low temperature. Ideal gases are a simplified model.
    • The provided pages contain various example problems applying gas laws to determine different properties, including volume, pressure, moles, and mass.

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    Description

    Explore the fascinating properties and behaviors of gases in this quiz based on Chemistry Chapter 5. Understand key concepts such as the ideal gas law, partial pressure, and the kinetic theory of gases. Test your knowledge on how gases behave under different conditions.

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