1.8 Thermodynamics Flashcards
(15 cards)
Define 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 under is standard conditions
examples :
Na (s) -> Na(g)
½ O2(g) -> O (g)
Define second ionisation energy
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.
Define 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, under standard conditions
example :
O (g) + e- -> O- (g)
Define second electron affinity
The second electron affinity is the enthalpy change when one
mole of gaseous 1- ions gains one electron per ion to produce gaseous 2- ions, under standard conditions
example
O - (g) + e- -> O2- (g
Define lattice formation enthalpy
The enthalpy change when one mole of solid ionic compound is formed from its gaseous ions under standard conditions
Na+(g) + Cl- (g) -> NaCl (s)
Why is first electron affinity exothermic
This is because the ion is more stable than the
atom, and there is an attraction between the nucleus and the
electron.
Why is second electron affinity endothermic
because it take energy to overcome the repulsive force between the negative ion and the electron.
Define enthalpy of hydration
Enthalpy change when one mole of gaseous ions become
aqueous ions under standard conditions
Define enthalpy of solution
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 under standard conditions
NaCl (s) + aq ->
Na+(aq) + Cl-(aq)
Difference between theoretical and Born Haber lattice enthalpies
The Born Haber lattice enthalpy is the real experimental value.
Born haber takes covalent character into account
