ENERGY CHANGES IN FORMING IONIC SUBSTANCES
The lattice energy of an ionic crystals is the heat of formation for one mole of
the ionic compound from gaseous ions under standard conditions. Thus, the
lattice energy of sodium chloride corresponds to the process:
Na+ (g) + Cl- (g) Na+ Cl- (s) H latt (Na+Cl-(s))
Lattice energies cannot be determined directly, but values can be obtained
indirectly by means of an energy cycle connecting the ionic solid, the gaseous
ions and the elements in their standard states.
H×
Na (s) + ½ Cl2 (g) Na+ (g) + Cl- (g)
HfO (Na+ Cl- (s)) H latt (Na+ Cl- (s))
Na+ Cl- (s)
Since HfO, the standard heat of formation of sodium chloride can be
measured conveniently in a calorimeter, H latt can be obtained if H× can
be found.
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The lattice energy of an ionic crystals is the heat of formation for one mole of
the ionic compound from gaseous ions under standard conditions. Thus, the
lattice energy of sodium chloride corresponds to the process:
Na+ (g) + Cl- (g) Na+ Cl- (s) H latt (Na+Cl-(s))
Lattice energies cannot be determined directly, but values can be obtained
indirectly by means of an energy cycle connecting the ionic solid, the gaseous
ions and the elements in their standard states.
H×
Na (s) + ½ Cl2 (g) Na+ (g) + Cl- (g)
HfO (Na+ Cl- (s)) H latt (Na+ Cl- (s))
Na+ Cl- (s)
Since HfO, the standard heat of formation of sodium chloride can be
measured conveniently in a calorimeter, H latt can be obtained if H× can
be found.
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