Lattice Enthlapy Flashcards
What is the Enthlapy of formation?
When one mole of products is formed
Exothermic
What is Enthlapy of combustion?
Complete combustion
1 mole of reactant burned
Exothermic
What is Ionisation Enthlapy?
The Enthlapy change for the conversion of 1 mole gaseous atoms to 1 mole of gaseous atoms, each atom losing an electron.
Endothermic
What is the Enthlapy of electron affinity?
The Enthlapy change for the conversion of one mole of gaseous atoms to one mole of gaseous anions, each atom gaining one electron.
First electron affinity is EXOTHERMIC
E.g. Cl (g) + e^- = Cl^-
Second electron affinity is ENDOTHERMIC
O^-(g) + e^- = O^2-
Why is the second electron affinity endothermic?
Electrons are added to an already negative ion
So it will repel and need energy
What is the second electron affinity?
The Enthlapy change for the conversion of one mole of gaseous 1- ions by gaining one electron.
What is Enthlapy of atomisation?
The Enthlapy change when one mole of gaseous atoms of a substance formed from the substance in its standard state.
E.g. 0.5 Cl2 = Cl (g)
Endothermic
What is bond dissociation enthalpy?
The Enthlapy change for breaking one mole of bonds in 1 mole of gaseous molecules.
Cl2 = Cl (g) + Cl (g)
Endothermic
What is lattice formation of Enthlapy?
Enthalpy change for the formation of one mole of solid ionic compound from its constituent gaseous atoms.
E.g. Na^+ (g) + Cl^- (g) = NaCl (s)
EXOTHERMIC
What is lattice dissociation enthalpy?
Enthalpy change when one mole of an ionic lattice dissociates into isolated gaseous ions.
E.g. NaCl (s) = Na ^+ (g) + Cl^- (g)
Endothermic
What is Enthlapy if hydration?
The Enthlapy change when one mole of gaseous ion dissolves in (an excess of) water (to give an infinitely dilute solution l)
EXOTHERMIC
E.g. Na^+ (g) = Na^+ (aq)
What is Enthlapy of Solution?
The Enthlapy change when one mole of solute dissolves in (an excess of) solvent (to give an infinitely dilute solution).
E.g. NaCl (s) = NaCl (aq)
EXOTHERMIC
What are the factors affecting lattice formation enthalpy?
- The HIGHER the charge, increases formation enthalpy.
- Small size of ion, increases lattice formation enthalpy.
Smaller ions have greater attraction for each other due to high charge density.
Therefore, more energy required to separate oppositely charged ions
Therefore larger enthalpy.
Exothermic and Endothermic
Exothermic
Value in Haber cycle stable
Bond formed
Negative values
Endothermic
Value in Haber cycle unstable
Bonds broken
Positive values
Describe the Born-Haber cycle.
Measures lattice enthalpy.
- Enthalpy change of formation
- Enthalpy of atomisation of a METAL
- Enthalpy of atomisation of a NON-METAL
- Enthalpy of ionisation of metal
- Electron affinity of gas
- Lattice enthalpy of formation
