Thermodynamics

• What are Born-Haber cycles used for?

  To determine enthalpy changes indirectly
• What are lattice enthalpies used for?

  They are used for ionic substances
• What is lattice dissociation enthalpy?

  Energy to break ionic lattice into ions
• How is lattice formation enthalpy defined?

  Energy to form ionic lattice from ions
• What is atomisation enthalpy?

  Energy for forming gaseous atoms
• What does the enthalpy of electron affinity represent?

  Enthalpy change when adding electrons
• How are different enthalpy changes combined?

  To produce a Born-Haber cycle

  
• What happens to the sign of an enthalpy change when the cycle counters the arrow direction?

  The sign of the enthalpy change is reversed
• How is lattice enthalpy calculated in a Born-Haber cycle?

  By following the cycle from start to finish
• What is the enthalpy of solution?

  Change when ionic solid dissolves in water
• What is the enthalpy of hydration?

  Change when gaseous ions dissolve in water
• Why is the enthalpy of hydration usually negative?

  Water attracts negative ions due to polarity
• What assumptions does the perfect ionic model make?

  All ions are perfectly spherical and non-covalent
• What is entropy a measure of?

  Disorder in a system
• How does temperature affect entropy?

  Entropy increases as temperature increases
• Which state of matter has the greatest entropy?

  Gases
• What happens to entropy during melting or evaporation?

  There is a sudden increase in entropy
• How is overall entropy change for a reaction measured?

  In JK$-1$mol$-1$
• What is true for all spontaneous reactions regarding entropy?

  They have a positive entropy value
• What does Gibbs Free-Energy (∆G) allow us to find?

  It allows finding ∆S without measuring surroundings

  
• What units is free-energy measured in?

  kJmol$-1$
• How can the Gibbs Free-Energy equation be represented graphically?

  As a straight line graph of ∆G against ∆S

  
• What is the significance of a negative ∆G?

  Indicates a spontaneous reaction
• What happens to the feasibility of a reaction if temperature changes?

  It changes the feasibility of the reaction