22.1 Enthalpy Changes Flashcards
What is lattice enthalpy of formation?
ENTHALPY CHANGE
1 MOLE of a solid IONIC compound
is formed from GASEOUS IONS.
Cation(g) + Anion(g) ⟶ 1 mol solid Ionic Compound
What is lattice enthalpy of dissociation?
ENTHALPY CHANGE
1 MOLE of solid IONIC compound
DISSOCIATES into its GASEOUS IONS
1 mol solid Ionic Compound ⟶ Cation(g) + Anion(g)
What is a born-haber cycle?
ENERGY CYCLE
for INDIRECT determination
of enthalpy change
What is the route for standard state elements ⟶ solid ionic lattice?
standard state elements
gaseous atoms
gaseous ions
solid ionic lattice
What are the energy changes for lattice enthalpy?
FORMATION
ATOMISATION
IONISATION + ELECTRON AFFINITY
LATTICE ENTHALPY
What is enthalpy change of FORMATION?
ENTHALPY CHANGE
1 mole of compound
is formed from STANDARD STATE ELEMENTS
Element in standard state ⟶ 1 mol compound
What is enthalpy change of ATOMISATION?
ENTHALPY CHANGE
1 mole of GASEOUS ATOMS
formed from STANDARD STATE ELEMENT
Element in standard state ⟶ 1 mol gaseous ions
What is first ionisation energy?
ENTHALPY CHANGE
1 ELECTRON REMOVED
from EACH ATOM
in 1 mol of GASEOUS ATOMS
to form 1 mol of GASEOUS 1+ IONS
What is first electron affinity?
ENTHALPY CHANGE
1 ELECTRON ADDED
to EACH ATOM
in 1 mol of GASEOUS 1- IONS
Is the first electron affinity exothermic or endothermic and why?
1st electron affinity = exothermic
atom wants to gain electron to become full outer shell
Is the second electron affinity exothermic or endothermic and why?
2nd electron affinity = endothermic
energy required to add electron OVERCOME REPULSION between electron + 1- anion
What factors affect lattice enthalpy of formation?
IONIC RADIUS
- bigger ionic radius = weaker ELECTROSTATIC ATTRACTION between oppositely charged ions - less energy released during formation >> less exothermic lattice enthalpy.
IONIC CHARGE
- greater charged ions = stronger ELECTROSTATIC ATTRACTION between oppositely charged ions - more energy released during formation = more exothermic lattice enthalpy
Is lattice enthalpy of formation endothermic or exothermic?
lattice enthalpy of formation = exothermic
- ionic bonds only formed between oppositely charged ions, so energy is released.
Is lattice enthalpy of dissociation endothermic or exothermic?
lattice enthalpy of dissociation = endothermic
- ionic bonds only broken between oppositely charged ions, so energy absorbed.
Is enthalpy change of formation endothermic or exothermic?
enthalpy change of formation = exothermic
- ionic bonds only formed
