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Entropy Calculations: Phase Changes quiz #1

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  • Which phase changes result in an increase in entropy?
    Both vaporization (liquid to gas) and fusion (melting, solid to liquid) result in an increase in entropy because they involve a transition to a more disordered state.
  • What is the formula for calculating the change in entropy during vaporization?
    The change in entropy during vaporization is calculated as ΔSvap = ΔHvap / T. Here, ΔHvap is the enthalpy of vaporization and T is the boiling point temperature in Kelvin.
  • What is the formula for calculating the change in entropy during fusion?
    The change in entropy during fusion is ΔSfus = ΔHfus / T. ΔHfus is the enthalpy of fusion and T is the melting point temperature in Kelvin.
  • Why must temperature be in Kelvin when using entropy and enthalpy formulas for phase changes?
    Temperature must be in Kelvin because thermodynamic equations require absolute temperature to ensure correct proportionality. Using Celsius or Fahrenheit would yield incorrect results.
  • What units are typically used for entropy in phase change calculations?
    Entropy is typically expressed in units of joules per Kelvin (J/K). This unit reflects the energy change per degree of temperature.
  • What units are commonly used for enthalpy in vaporization and fusion calculations?
    Enthalpy is usually given in joules (J) or kilojoules (kJ). These units measure the heat involved in the phase change.
  • Which two phase changes specifically involve liquids and are discussed in entropy calculations?
    Vaporization (liquid to gas) and fusion (solid to liquid) both involve liquids. These are the main phase changes considered for entropy calculations in this context.
  • How do the formulas for ΔSvap and ΔSfus connect entropy and enthalpy?
    Both formulas show that entropy change is directly proportional to the enthalpy change and inversely proportional to temperature. This relationship links the energy required for phase change to the resulting disorder.
  • What must you always check about the temperature value before using it in entropy calculations for phase changes?
    You must ensure the temperature is in Kelvin before using it in the formulas. This is necessary for accurate and meaningful results.
  • Why are vaporization and fusion the primary focus when discussing entropy changes involving liquids?
    Vaporization and fusion are the primary focus because both involve a liquid phase either as a starting or ending state. These transitions are key for understanding entropy changes related to liquids.