22.1 Enthalpy Changes
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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
Is enthalpy change of atomisation endothermic or exothermic?
atomisation = endothermic • energy required to overcome intermolecular forces/break covalent bonds