HM THERMODYNAMICS

• Enthalpy change


  Heat energy change at constant pressure
• is enthalpy change +ve or -ve


  either
• -ve enthalpy change is

  exothermic
• +ve enthalpy change is

  endothermic
• enthalpy of formation


  Enthalpy change when one mole of a substance is formed from its constituent elements with all substances in their standard states.
• is enthalpy of formation +ve or -ve?


  mostly -ve
• Enthalpy of combustion


  Enthalpy change when one mole of a substance undergoes complete combustion in oxygen with all substances in standard states.
• is enthalpy of combustion +ve or -ve


  -ve
• Enthalpy of atomisation


  Enthalpy change when one mole of gaseous atoms is produced from an element in its standard state.
• is enthalpy of atomisation +ve or -ve


  +ve
• equation for atomisation energy of chlorine

  1/2 Cl2 (g) --> Cl2 (g)
• First ionisation energy


  Enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions.
• equation for the first ionisation energy using X


  X(g) -> X+(g) + e-
• Second ionisation energy


  Enthalpy change when each ion in one mole of gaseous 1+ ions loses one electron to form one mole of gaseous 2+ ions.
• equation for second ionisation energy using X

  X+(g) -> X2+(g) + e-
• are ionisation energies +ve or -ve


  +ve
• First electron affinity


  Enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions.
• equation for first electron affinity using X

  X(g) + e- --> X-(g)
• Second electron affinity


  Enthalpy change when each ion in one mole of gaseous 1- ions gains one electron to form one mole of gaseous 2- ions.
• equation for second electron affinnity using X


  X-(g) + e- --> X2-(g)
• is 1st EA +ve or -ve


  -ve
• is 2nd EA +ve or -ve

  +ve (as adding -ve electron to -ve ion)
• Lattice enthalpy of formation

  Enthalpy change when one mole of a solid ionic compound is formed from into its constituent ions in the gas phase.
• is LEF +ve or -ve


  -ve
• equation for enthalpy of formation of NaCl

  Na+(g) + Cl- (g) → NaCl(s)
• equation for enthalpy of formation of MgCl2

  Mg2+(g) + 2Cl- (g) → MgCl2(s)
• Lattice enthalpy of dissociation

  Enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in the gas phase
• is LED +ve or -ve


  +ve
• Enthalpy of hydration


  Enthalpy change when one mole of gaseous ions become hydrated and form aqueous ions (dissolved in water).
• equation for enthalpy of hydration of Na

  Na+(g) + aq → Na+(aq)
• equation for enthalpy of hydration of Cl- in NaCl


  Cl-(g) + aq --> Cl- (aq)
• is enthalpy of hydration +ve or -ve


  -ve
• Enthalpy of solution


  Enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other.
• is enthalpy of solution +ve or -ve


  either
• equation for enthalpy of solution of NaCl

  NaCl(s) + aq → Na+(aq) + Cl-(aq)
• Bond dissociation enthalpy


  Enthalpy change when one mole of covalent bonds is broken in the gaseous state.
• is bond dissociation enthalpy +ve or -ve


  +ve
• mean bond enthalpy


  Enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form two free radicals, averaged over a range of compounds.
• is mean bond enthalpy +ve or -ve


  either
• enthalpy of vaporisation


  Enthalpy change when one mole of a liquid is turned into a gas