Enthalpy + Entropy

• What is the definition of entropy?

  A measure of energy dispersal in a system
• What is the symbol for entropy?

  S
• Which state of matter is more disordered, solid or gas?

  Gas
• What is the unit of standard entropy?

  J K-1 mol-1
• How does temperature affect entropy?

  Higher temperature increases particle movement and randomness
• What happens to entropy when a solid ionic lattice is dissolved in solution?

  Entropy increases due to more disorder
• How does the change in the number of gas molecules affect entropy?

  More gas molecules increase entropy; fewer decrease it
• What is the equation used to calculate entropy change?

  ΔS = S final - S initial

  
• What is the Gibbs' free energy equation?

  ΔG = ΔH - TΔS

  
• What does ΔG represent in the Gibbs' free energy equation?

  The change in free energy of a system

  
• What does ΔH represent in the Gibbs' free energy equation?

  The change in enthalpy of a system

  
• What does ΔS represent in the Gibbs' free energy equation?

  The change in entropy of a system

  
• What are the conditions for spontaneous change based on ΔH, ΔS, and ΔG?

  • ΔH negative, ΔS positive: Always negative ΔG (Reaction feasible)
  • ΔH negative, ΔS negative: Negative ΔG at low temperatures (Feasible at low temp)
  • ΔH positive, ΔS negative: Always positive ΔG (Reaction never feasible)
  • ΔH positive, ΔS positive: Negative ΔG at high temperatures (Feasible at high temp)
• For a reaction to occur spontaneously, must ΔG be positive or negative?

  Negative
• What are the limitations of predictions of feasibility made by using ΔG?

  • High activation energy may prevent reaction
  • Rate of reaction may be very slow