Calculate the lattice energy for CaF 2. The sublimation energy for Sr is 164 kJ/mol, E i1 = +549.5 kJ/mol, E i2 = +1064.2 kJ/mol, E ea for Cl (g) = -348.6 kJ/mol, energy for the formation of one mole of SrCl 2 from its elements = -803.7 kJ/mol, and the bond dissociation energy for Cl 2 (g) = +243 kJ/mol.Įxercise 5. Which has the highest lattice energy, Na 3P or Na 2S?Įxercise 4. Order the following ionic compounds from lowest to highest lattice energy. What is the lattice energy for MgF 2?Įxercise 2. Consider the following Born-Haber cycle for MgF 2. A more extensive list can be found in other tables or in the Handbook of Physics and Chemistry.Įxercise 1. In the case of NaCl and MgCl 2, the MgCl 2 has the larger lattice energy because the magnesium cation is smaller, and the charge is a +2 rather than a +1 for the sodium ion.īelow is a table with the lattice energies of some ionic compounds. The Born-Haber cycle may also be used to calculate any one of the other quantities in the equation for lattice energy, provided that the remainder is known. This is because the charges are the same, but the potassium ion is larger than the sodium ion. For cesium chloride, using this data, the lattice energy is: Hlattice (411+109+122+496+368)kJ 770kJ H lattice ( 411 + 109 + 122 + 496 + 368) kJ 770 kJ. For example, the lattice energy of NaCl is larger than the lattice energy of KCl. The strength of the bond between the ions of opposite charge in an ionic compound. Lattice energies are large when ions are closer together, the distance between the ions is small and when the charges are larger. Lattice Energies and the Strength of the Ionic Bond. Coulomb’s law is equal to a constant, k, multiplied by the product of the ion charges, z 1 and z 22, between the ions. Recall, lattice energy is positive meaning it is endothermic. The stronger the bond, the higher the lattice energy. A high negative value of lattice energy indicates that the formation of NaCl is highly favored.
Lattice energy, E lattice is dependent on the strength of the bond between the cation and anion in an ionic bond. The value of its lattice energy is -787 kJ/mol. The lattice energy is always positive, because it takes energy to separate the ions from the solid. The equation for the lattice energy is the reverse of the equation in Step 5 in the figure below, for the formation of the solid from its ions which releases 787 kJ/mol of energy.Ī Born-Haber cycle allows the calculation of the lattice energy for a solid ionic compound. In 1918, Born and Lande proposed an equation to derive lattice energy from the repulsive potential energy term and the electric potential of the ionic lattice. The process absorbs energy, and is highly endothermic.
Lattice energy equation series#
Lattice energy, E lattice is the energy required to separate one mole of a solid ionic compound into its gaseous ions. Furthermore, a series of empirical equations were derived, relating several acid-base parameters with lattice energy.