Definitions

• What is the enthalpy of atomisation?

  The enthalpy of atomisation of an element is the enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state under standard conditions
• What is bond dissociation enthalpy?

  The bond dissociation enthalpy is the standard molar enthalpy change when one mole of a covalent bond is broken into two gaseous atoms
• What happens during the first ionisation enthalpy?

  The first ionisation enthalpy is the enthalpy change required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a +1 charge
• What does the second ionisation enthalpy involve?

  The second ionisation enthalpy is the enthalpy change to remove 1 mole of electrons from one mole of gaseous 1+ ions to produces one mole of gaseous 2+ ions
• What is the first electron affinity?

  The first electron affinity is the enthalpy change that occurs when 1 mole of gaseous atoms gain 1 mole of electrons to form 1 mole of gaseous ions with a –1 charge
• Why is the first electron affinity exothermic for certain atoms?

  because the ion is more stable than the atom, and there is an attraction between the nucleus and the electron.
• What does the second electron affinity involve?

  the enthalpy change when one mole of gaseous 1- ions gains one electron per ion to produce gaseous 2- ions.
• Why is the second electron affinity for oxygen endothermic?

  because it takes energy to overcome the repulsive force between the negative ion and the electron
• What is the enthalpy of lattice formation?

  The Enthalpy of lattice formation is the standard enthalpy change when 1 mole of an ionic lattice is formed from its constituent ions in gaseous form
• What is the enthalpy of lattice dissociation?

  The Enthalpy of lattice dissociation is the standard enthalpy change when 1 mole of an ionic crystal lattice form is separated into its constituent ions in gaseous form
• What is the enthalpy of hydration?

  Enthalpy change when one mole of gaseous ions become aqueous ions. This always gives out energy (exothermic, -ve) because bonds are made between the ions and the water molecules.
• What is the enthalpy of solution?

  The enthalpy of solution is the standard enthalpy change when one mole of an ionic solid dissolves in a large enough amount of water to ensure that the dissolved ions are well separated and do not interact with one another