AQA A level Chemistry – Thermodynamics Review Questions and Answers

What are standard conditions? 298K/25°C 100kPa/1 atm 1 moldm-3 Enthalpy change of formation The enthalpy change when 1 mole of a compound is formed from its constituent elements under standard conditions, with all reactants and products in their standard states. Enthalpy change of combustion The enthalpy change when 1 mole of a substance is burned completely in oxygen. Enthalpy change of atomisation The enthalpy change that accompanies the formation of 1 mole of gaseous atoms from the element in its standard state. First ionisation enthalpy The enthalpy change when 1 mole of gaseous atoms loses 1 electron per atom to form 1 mole of gaseous 1+ ions. Second ionisation enthalpy The enthalpy change when 1 mole of gaseous 1+ ions loses 1 electron per atom to form 1 mole of gaseous 2+ ions. First electron affinity The enthalpy change when 1 mole gaseous atoms gains 1 electron per atom to form 1 mole of gaseous 1- ions. Second electron affinity The enthalpy change when 1 mole of gaseous 1- ions gains 1 electron per atom to form 1 mole of gaseous 2- ions. Mean bond enthalpy The enthalpy change when 1 mole of gaseous molecules each breaks a covalent bond to form 2 gaseous ions or free radicals. Lattice enthalpy of formation The enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions. Lattice enthalpy of dissociation The enthalpy change when 1 mole of a solid ionic compound dissociates into its gaseous ions. Enthalpy of hydration The enthalpy change when 1 mole of gaseous ions dissolves completely in water.