chem energetics

• enthalpy change of atomisation:

  • energy required to form 1 mole of gaseous atoms from the element in its standard state under standard conditions
  • energy required to form gaseous atoms from 1 mole of the compound in its standard state under standard conditions
• Bond energy: average energy required to break 1 mole of covalent bond between 2 atoms in gaseous state
• enthalpy change of combustion: energy released when 1 mole of substance is completely burnt in excess oxygen under standard conditions
• enthalpy change of formation: enthalpy change when one mole of a substance is formed from its constituent elements in their standard states under standard conditions
• enthalpy change of hydration: energy released when one mole of free gaseous ions is hydrated under standard conditions

  • ion-dipole interactions between gaseous ions and water molecules are formed during hydration
  • ion (aq) formed from ion (g)
• lattice energy: energy released when 1 mole of solid ionic compound is formed from its constituent gaseous ions
• enthalpy change of neutralisation: energy released when 1 mole of water is formed in a neutralisation reaction between an acid and a base under standard conditions
• enthalpy change of solution: energy change when 1 mole of substance is completely dissolved in an infinite volume of solvent under standard conditions

  • involves hydration and thus forming of ion-dipole interactions
  • sol = hyd - LE
• 1st electron affinity: energy change when 1 mole of electrons is added to 1 mole of gaseous atoms to form 1 mole of single charged gaseous anions
• 1st ionisation energy: energy absorbed when 1 mole of electrons is removed from 1 mole of gaseous atoms to form 1 mole of singly charged gaseous cations