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Entropy quiz

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Terms in this set (15)

  • What does entropy (S) represent in thermodynamics?
    Entropy measures the disorder, randomness, or chaos within a system, its surroundings, or the universe.
  • What does the second law of thermodynamics state about entropy?
    The second law states that molecular systems tend to move spontaneously toward maximum disorder, meaning the entropy of the universe increases over time.
  • What is the third law of thermodynamics regarding entropy?
    The third law states that at absolute zero (0 Kelvin), the entropy of all objects is zero.
  • How does entropy change when a substance goes from solid to liquid to gas?
    Entropy increases as molecules become more spaced out and disordered, so the sign of entropy change (ΔS) is positive.
  • What happens to entropy when a gas condenses to a liquid and then freezes to a solid?
    Entropy decreases as molecules become more ordered, so the sign of entropy change (ΔS) is negative.
  • How do you calculate the total entropy change (ΔS_total) for a reaction?
    ΔS_total equals ΔS_system plus ΔS_surroundings, representing the entropy change of the universe.
  • What does a positive ΔS_total indicate about a reaction's spontaneity?
    A positive ΔS_total means the reaction is spontaneous.
  • How do you calculate the standard entropy change (ΔS) of a reaction?
    ΔS is calculated as the sum of the entropies of products minus the sum of the entropies of reactants, using their coefficients.
  • What is the standard molar entropy (S°) and how does it vary with state of matter?
    Standard molar entropy is the entropy of one mole of a substance at standard conditions; gases have the highest entropy, followed by liquids, then solids.
  • For elements in their natural state, when is ΔS equal to zero?
    ΔS is only zero at absolute zero (0 Kelvin), according to the third law of thermodynamics.
  • What is Troughton's Rule regarding entropy of vaporization?
    Troughton's Rule states that the entropy of vaporization for many substances is about 88 J/(mol·K) when transitioning from liquid to gas.
  • What formula relates entropy change (ΔS), enthalpy change (ΔH), and temperature (T) during vaporization?
    ΔS = ΔH / T, where ΔH is enthalpy of vaporization and T is temperature in Kelvin.
  • What is the Boltzmann equation for entropy change?
    The Boltzmann equation is ΔS = k × ln(W), where k is the Boltzmann constant and W is the number of microstates or work.
  • How do you convert work from liters·atmospheres to joules for entropy calculations?
    Multiply the value in liters·atmospheres by 101.3 to convert to joules.
  • What is the value of the Boltzmann constant (k) used in entropy calculations?
    The Boltzmann constant is 1.38 × 10⁻²³ J/K.