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Entropy quiz #1

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Terms in this set (39)

  • A decrease in entropy is associated with which type of reaction?
    A decrease in entropy is associated with reactions where order increases, such as condensation or freezing.
  • What types of processes have a negative ΔS?
    Processes like freezing, condensation, or deposition have a negative ΔS because they result in decreased disorder.
  • What happens to the total entropy of the universe during spontaneous processes?
    The total entropy of the universe always increases for spontaneous processes, according to the second law of thermodynamics.
  • What kind of reactions result in an increase in the entropy of the system?
    Reactions that produce more moles of gas or convert solids to liquids or gases result in increased entropy.
  • Which has the highest entropy?
    Gases have the highest entropy compared to liquids and solids.
  • Which state of matter has the highest entropy?
    The gaseous state has the highest entropy.
  • What is the entropy of a perfect crystal at absolute zero?
    A perfect crystal at absolute zero has zero entropy, according to the third law of thermodynamics.
  • If the heat of fusion for water is 6 kJ/mole, what is the entropy of fusion?
    The entropy of fusion is ΔS = ΔH/T; for water, ΔS = 6000 J/mol ÷ 273 K ≈ 22 J/mol·K.
  • What types of reactions are associated with a decrease in entropy?
    A decrease in entropy is associated with reactions where gases become liquids or solids, or when fewer moles of gas are produced.
  • Which phase change results in an increase in entropy?
    Melting (solid to liquid), vaporization (liquid to gas), and sublimation (solid to gas) all result in increased entropy.
  • What are the signs of ΔS for processes where disorder increases?
    The sign of ΔS is positive when disorder increases.
  • What kind of substance has the largest molar entropy?
    A complex, heavy gas would have the largest molar entropy.
  • What factors can result in an increase in the entropy of a system?
    Increasing temperature, increasing molecular complexity, increasing mass, and increasing the number of moles all increase entropy.
  • Entropy increases from solid to liquid to gas. Why?
    Because molecular motion and disorder increase as substances move from solid to liquid to gas.
  • Which process is expected to have an increase in entropy?
    Processes like melting, vaporization, or dissolution are expected to have increased entropy.
  • When disorder in a system increases, what happens to entropy?
    Entropy increases when disorder in a system increases.
  • What does entropy measure?
    Entropy measures the degree of disorder or randomness in a system.
  • During which phase change does the entropy of a sample of H2O increase?
    Entropy increases during melting (ice to liquid) and vaporization (liquid to gas) of H2O.
  • Does the entropy of the surroundings increase for spontaneous processes?
    Yes, the entropy of the surroundings often increases for spontaneous processes, contributing to the overall increase in universal entropy.
  • Which processes result in an increase in entropy of the system?
    Processes such as melting, vaporization, sublimation, and reactions producing more gas molecules increase system entropy.
  • Which phase has the highest entropy?
    The gas phase has the highest entropy.
  • Which processes have a positive change in entropy (ΔS > 0)?
    Processes like melting, vaporization, and dissolution have ΔS > 0.
  • What happens to the entropy of a sample of matter when it changes state from a solid to a liquid?
    The entropy increases when a sample changes from solid to liquid.
  • Which process results in the increase in entropy of the universe?
    Any spontaneous process results in an increase in the entropy of the universe.
  • What kind of processes represent an increase in entropy?
    Processes where disorder increases, such as solid to liquid or liquid to gas, represent an increase in entropy.
  • Which process involves an increase in entropy?
    Processes like melting, vaporization, and dissolution involve an increase in entropy.
  • Which change will occur in a system with increasing entropy?
    The system will become more disordered as entropy increases.
  • Which process involves a decrease in entropy?
    Processes like freezing, condensation, and deposition involve a decrease in entropy.
  • What happens to the entropy of a system during condensation?
    The entropy decreases during condensation because the system becomes more ordered.
  • What is the entropy of a solid based on?
    The entropy of a solid is based on its molecular arrangement and motion; at absolute zero, it is zero for a perfect crystal.
  • What is the absolute entropy of a system with only one possible arrangement of its atoms?
    The absolute entropy is zero if there is only one possible arrangement, as in a perfect crystal at absolute zero.
  • What types of processes involve a decrease in entropy?
    Processes like freezing, condensation, or reactions forming fewer moles of gas involve a decrease in entropy.
  • Which reactions have a positive ΔS_rxn?
    Reactions that produce more moles of gas or increase disorder have a positive ΔS_rxn.
  • Which process is necessarily driven by an increase in the entropy of the surroundings?
    Endothermic processes at high temperature are driven by an increase in the entropy of the surroundings.
  • How does the entropy of steam compare to the entropy of ice?
    Steam (gas) has much higher entropy than ice (solid).
  • What happens to the entropy of a piece of wood as it is burned?
    The entropy increases as wood burns, producing gases and increasing disorder.
  • What happens to the entropy of a bucket of water as it is cooled down (but not frozen)?
    The entropy decreases as the water is cooled, because molecular motion decreases.
  • Which of these species would you expect to have the lowest standard entropy (S°)?
    A simple, light solid (like diamond or sodium) would have the lowest standard entropy.
  • When ice, H2O(s), melts at 0°C, entropy increases because the molecules
    The molecules gain freedom of movement and become less ordered as ice melts.