8. Thermodynamics

• Enthalpy Change of Reaction


  The number of moles of reactant specified in the balanced equation reacting together
• Enthalpy of Formation


  The enthalpy change required to form one mole of a substance from its constituent elements under standard conditions in standard states
• Enthalpy of Combustion

  The enthalpy change required to completely burn one mole of a substance in the presence of oxygen, with all substances in their standard states
• First Ionisation Enthalpy


  The enthalpy change when one mole of gaseous atoms loses one electron per atom to produce gaseous +1 ions
• Second Ionisation Enthalpy


  The enthalpy change when one mole of gaseous +2 ions are formed from one mole of +1 ions
• First Electron Affinity


  The enthalpy change when one mole of gaseous atoms gains one electron per atom to produce gaseous -1 ions
• Second Electron Affinity


  The enthalpy change when one mole of gaseous -1 ions gains one electron per ion to form gaseous -2 ions
• Enthalpy of Atomisation

  The enthalpy change when one mole of gaseous atoms are produced from an element in its normal state
• Hydration Enthalpy


  The enthalpy change when one mole of gaseous ions become hydrated (dissolved in water)
• Enthalpy of Solution

  The enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are far apart enough to not interact with one another
• Bond Dissociation Enthalpy


  The enthalpy change when one mole of covalent bonds are broken in the gaseous state
• Lattice Enthalpy of Formation


  The enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase
• Lattice Enthalpy of Dissociation


  The enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in the gas phase
• Hess's Law


  The sum of energy changes in the clockwise direction is always equal to the energy changes in the anticlockwise direction of a Hess's Cycle
• Hess's Cycle


  A physical representation of the different pathways by which our desired product can be formed, including the enthalpy of formation and enthalpy of combustion

  
• Born-Haber Cycle


  A physical representation of a complete reaction and the numerous stages involved to calculate a enthalpy value

  
• Enthalpy of Formation BHC

  The sum of all other enthalpy diagrams in a Born-Haber cycle. This value is always negative
• Positive


  Are the following values positive of negative?- Enthalpy of atomisation- Ionisation enthalpies- Enthalpy of vapourisation- Second electron affinity- Lattice enthalpy of dissociation
• Negative


  Are the following values positive of negative?- First electron affinity- Lattice enthalpy of formation- Enthalpy change of reaction
• M (s) --> M (g)

  enthalpy of atomisation of a metal
• 1/2 X2 --> X (g)


  enthalpy of atomisation of a diatomic
• Cl2 --> 2 Cl (g)


  Bond dissociation enthalpy of chlorine
• Na+ (g) + Cl- (g) --> NaCl (s)

  Formation lattice enthalpy of sodium chloride
• NaCl(s) --> Na+ (g) + Cl- (g)


  Dissociation lattice enthalpy of sodium chloride
• CH3CH2OH (l) + 3O2 (g) --> 2CO2 (g) + 3H2O (l)


  enthalpy of combustion of ethanol
• X (g) --> X+ (g) + e-


  1st ionisation enthalpy
• X+ (g) --> X2+ (g) + e-


  2nd ionisation enthalpy
• X (g) + e- --> X- (g)


  1st electron affinity
• X- (g) + e- --> X2- (g)


  2nd electron affinity
• H2O (l) --> H2O (g)

  enthalpy of vaporisation of H2O
• H2O (s) --> H2O (l)

  enthalpy of fusion of H2O