thermodynamics

• What are Born-Haber cycles similar to?

  Hess’s Law
• What do Born-Haber cycles allow us to determine?

  Enthalpy changes that cannot be measured directly
• What are lattice enthalpies used for?

  Ionic substances
• How is lattice dissociation enthalpy defined?

  Energy to break ionic lattice into gaseous ions
• What is lattice formation enthalpy?

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

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

  Enthalpy change when adding electrons to gaseous atoms
• How are different enthalpy changes combined in Born-Haber cycles?

  Using a method similar to Hess’s Law

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

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

  By summing the enthalpy changes around the cycle

  
• What is the enthalpy of solution defined as?

  Enthalpy change when dissolving ionic solid in water
• What is the enthalpy of hydration?


  Enthalpy change when gaseous ions dissolve in water
• Why is the enthalpy of hydration nearly always negative?

  Water attracts negative ions due to its polarity
• What does the perfect ionic model assume about ions?

  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 when a substance melts or evaporates?

  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