Thus, formation of both Mg 2+ and O 2- ions requires very large amount of energy.
The Born-Haber cycle helps us in understanding the stability of many ionic compounds. Consequently, smaller size of the constituent ions results the greater lattice energy of the ionic solid. Smaller atoms feature smaller interatomic distances in the ionic lattice and stronger binding forces. Greater distance between the ions in a lattice causes the weaker the electrostatic forces holding them together, the lower the lattice energy. The lattice energy of an ionic compound is inversely proportional to the distance between the ions. As a consequence of this, the electrostatic forces of attraction are stronger in calcium chloride (than those in sodium chloride). This is because the magnitude of the positive charge held by the calcium cation (+2) is greater than that held by the sodium cation (+1). the greater the charge, the stronger the force of attraction, the stronger the lattice.įor example, the lattice energy of calcium chloride is greater than that of sodium chloride. The strength of the electrostatic force of attraction is directly proportional to the magnitude of the charge held by the constituent ions, i.e. In an ionic lattice, the individual ions are attracted to each other by the electrostatic forces between them. Lattice Energy depends on: Charge held by the Constituent Ions The molar lattice energy of an ionic crystal can be expressed in terms of molar lattice enthalpy, pressure, and change in volume via the following equation: Relation between Lattice Energy and Lattice Enthalpy U can be calculated if other quantities of the equation are known. The algebraic sum of the energy terms should be equal to the heat of formation (∆H f) of NaCl.As heat is actually evolve in the reaction, ∆H f will be negative. Calculation of the Change in Energy for the formation of NaCl (Born-Haber Cycle) According to Hess’ laws, if a chemical reaction takes place in one step or several steps the total heat of reaction is constant. The Born-Haber cycle is based on Hess’ law of constant heat of summation. It is a thermodynamic cycle correlating the heat of formation of a compound with other thermochemical quantities. The lattice energy of a ionic crystal is determined by the Born-Haber Cycle. Factors associated with the crystal geometry have to be included. 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. 
The lattice energy of sodium ion is approximately 778kJ mol -1.This is an endothermic process.
#LATTICE ENERGY EQUATION FREE#
This is also the energy required to split one mole of crystalline substance into free gaseous ion. The lattice energy of an ionic solid is the energy released when 1 mole of the crystalline substance is formed from the free gaseous ion (i. Relation between Lattice Energy and Lattice Enthalpy.Calculation of the Change in Energy for the formation of NaCl (Born-Haber Cycle).
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