enthalpy change

• Exothermic


  Energy released to the environment, energy released from bond making greater than energy absorbed for bond breaking, reaction gets hotter.
• Endothermic


  Energy absorbed from the environment, energy absorbed for bond breaking greater than energy released from bond making, reaction gets colder.
• Standard conditions


  298 K, 100kPa, Solutions at 1M
• Standard states


  physical states under standard conditions
• Enthalpy change of reaction


  enthalpy change associated with a stated equation
• ΔrH

  Enthalpy change of reaction symbol
• Enthalpy change of formation


  formation of 1 mole of a compound from its elements
• ΔfH


  Enthalpy change of formation symbol
• Enthalpy change of combustion


  Complete combustion of 1 mol of a substance (excess oxygen)
• ΔcH


  Enthalpy change of combustion symbol
• Enthalpy change of neutralisation


  Formation of 1 mole of water from neutralisation reaction
• ΔneutH


  Enthalpy change of neutralisation symbol
• Average bond enthalpy


  Average energy required to break 1 mole of bonds in gaseous molecules
• Heat energy change


  q = mcΔT
• Molar enthalpy change


  ΔH = (-q÷1000) /moles
• Lattice enthalpy

  Formation of 1 mole of ionic lattice from gaseous ions.

  It can be used as a measure of the strength of ionic bonding in a giant ionic lattice
• ∆LEH


  Lattice enthalpy symbol
• First ionisation energy

  Energy required to remove one electron from each atom in a mole of gaseous atoms to form 1 mole of 1+ ions
• enthalpy change of atomisation


  Formation of 1 mole of gaseous atoms from the element in its standard state
• electron affinity


  Energy required or released when 1 electron is added to each atom in 1 mole of gaseous atoms to produce 1 mole of 1- ions.
• enthalpy change of solution


  Enthalpy change when dissolving of 1 mole of solute
• ∆solH


  enthalpy change of solution symbol
• enthalpy change of hydration


  Enthalpy change when dissolving of 1 mole of gaseous ions in water
• ∆hydH


  enthalpy change of hydration symbol