Lattice enthalpies Lattice enthalpy may be seen defined
Lattice enthalpies • Lattice enthalpy may be seen defined in two different ways, depending on the reference literature. • For the IB it is defined as the energy released when 1 mole of an ionic substance is formed from its constituent ions at infinite separation. • Na+ + Cl. Na. Cl(s) ΔH = -ve
Animation • Each ion exerts an electrostatic field that attracts the oppositely charged ions. • The ions are all drawn together into a giant lattice in which every positive ion is surrounded by negative ions and vice-versa. • The animation only shows the first few ions in the lattice, but the process continues until all of the ions formed in the reaction are arranged in rows and columns - a giant ionic lattice. • The energy released on forming the lattice is more than enough to compensate for any energy needed to ionise the sodium (in this case).
Comparison Lattice Enthalpies od different Ionic Compounds • How can we compare the effect of both the relative sizes and the charges of the ions on the lattice enthalpies of different ionic compounds. • The relative value of theoretical lattice enthalpy increases with higher ionic charge and smaller ionic radius due to increased forces of attraction.
Comparison Lattice Enthalpies od different Ionic Compounds
Comparison Lattice Enthalpies od different Ionic Compounds
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