Enthalpy/ born haber cycles

• Enthalpy change is the heat energy transferred in a reaction at constant pressure
• Enthalpy change of formation : the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions
• Enthalpy change of atomisation of an element: the enthalpy change when 1 mole of gasous atoms is formed from an element in its standard state
• Enthalpy change of atomisation of a compound: the enthalpy change when 1 mole of compound in its standard state is converted to gasous atoms
• First ionisation energy: the enthalpy change when 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms
• First electron affinity: the enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole gaseous atoms
• Enthalpy change of hydration: the enthalpy change when 1 mole aquesous ions is formed from 1 mole gaseous ions
• Enthalpy change of solution: the enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution.
• The enthalpy of hydration of fluoride ions is more negative than chloride ions; as fluorine= more charge dense the chlorine... stronger attraction of F- to H2O+ (IN WATER)...more energy required
• The second ionisation energy of calcium is greater than the first ionisation energy:

  • as electron removed from a positive ion
  • electron being removed from smaller ion (lower 2p subshell)/electron being removed is closer to the nucleus
  • stronger attraction between same number of protons/fewer electrons
  • .....more energy required to remove electron