5.2 Definitions (Enthalpy) Flashcards
Lattice dissociation enthalpy
The enthalpy change when 1 mol of solid ionic compound is completely dissociated into its constituent gaseous ions under standard conditions
ENDO
Lattice formation enthalpy
The enthalpy change when 1 mol of solid ionic compound is formed from its constituent gaseous ions under standard conditions
EXO
Atomisation energy
The energy required for the formation of 1 mol of gaseous atoms from an element in its standard state under standard conditions
ENDO
Enthalpy of electron affinity
The enthalpy change when 1 mol of electrons is added to 1 mol of gaseous atoms to form 1 mol of gaseous 1- ions under standard conditions
1st EXO, 2nd ENDO
First ionisation energy
The energy required to remove 1 mol of electrons from 1 mol of gaseous atoms to form 1 mol of gaseous 1+ ions
ENDO
Enthalpy change of hydration
The enthalpy change when 1 mol of a gaseous ion dissolves in water (e.g. Na+(g) –> Na+(aq)
EXO
Why is there an energy change when dissolving gaseous ions in water?
The polar nature of water stabilises the ions
The greater the charge density of the ion, the greater the affinity for water and the more exothermic the process will be
Enthalpy change of a solution
The enthalpy change when 1 mol of a solute completely dissolves in a water (e.g. NaCl(s) –> Na⁺(aq) + Cl⁻(aq)
EITHER EXO OR ENDO
Lattice dissociation enthalpy EXO OR ENDO?
Endothermic (breaking bonds uses energy)
Lattice formation enthalpy ENDO OR EXO?
Exothermic (formation of bonds releases energy)
Enthalpy of formation
The enthalpy change associated with the formation of 1 mole of a compound from its constituent elements in their standard states under standard conditions.
USUALLY EXO BUT CAN BE ENDO
Equation to find enthalpy change of solution
△sol H =△lat H + △hyd H
What is the basis of a Born-Haber Cycle?
Lattice enthalpy of formation (down) with gaseous constituent ions at the top and solid ionic compound at the bottom.
Enthalpy of formation is the starting point from bottom up
