Lattice Enthalpy
Lattice Enthalpy
The Lattice Enthalpy of an ionic solid is defined as the energy
required to completely separate one mole of a solid ionic compound into gaseous
constituent ions. For example, the lattice enthalpy of NaCl is 788kJ mol1. This
means that 788kJ of energy is required to separate one mole of solid NaCl into
one mole of Na+(g) and one mole of Cl (g) to an infinite distance.
This process involves both the attractive forces between ions of
opposite charges and the repulsive forces between ions of like charge. The
solid crystal being three-dimensional; it is not possible to calculate lattice
enthalpy directly from the interaction of forces of attraction and repulsion
only. Factors associated with the crystal geometry have to be included.
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