The Born-Haber cycle is a fundamental concept in chemistry that explains the energy changes during the formation of ionic compounds. It uses Hess's Law to calculate lattice enthalpy, a measure of the energy needed to separate one mole of an ionic solid into gaseous ions. Factors like ionic charges and ion sizes impact lattice enthalpy, with greater charges and smaller ions increasing it. The cycle also helps distinguish between ionic and covalent characteristics in bonds, based on the comparison of theoretical and experimental enthalpy values.
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Hess's Law allows for the computation of challenging enthalpy values, such as lattice enthalpy, by using a series of energy changes
Construction of the cycle
The Born-Haber cycle is constructed to determine the lattice enthalpy of an ionic compound
Application of Hess's Law
Hess's Law is applied to the steps of the Born-Haber cycle to calculate the lattice enthalpy
Insertion of known enthalpy values
The known enthalpy values for formation, atomization, ionization, and electron affinity are inserted into the Born-Haber cycle to calculate the lattice enthalpy
The lattice enthalpy of an ionic compound is determined by subtracting the sum of atomization enthalpies, ionization energy, and electron affinity from the enthalpy of formation
Greater ionic charges result in stronger electrostatic attractions and higher lattice enthalpies
Larger ions have more diffuse electron clouds, leading to weaker electrostatic attractions and lower lattice enthalpies
The lattice enthalpy of an ionic compound is affected by the ionic charges and sizes of its constituent ions, as seen in the comparison of sodium chloride and magnesium oxide
Minor discrepancies between theoretical and experimental lattice enthalpies suggest predominantly ionic bonding, while significant differences indicate covalent character
Covalent characteristics in ionic bonds arise when the electronegativity difference is insufficient for complete electron transfer, resulting in anion polarization
The degree of covalent character in an ionic bond is influenced by the cation's polarizing power and the anion's polarizability
Born-Haber calculations allow students to deepen their understanding of the energetics behind ionic compounds and their properties
Engaging with Born-Haber calculations allows students to explore both the experimental and theoretical aspects of lattice enthalpies
Born-Haber calculations help students understand the differences between ionic and covalent bonding in ionic compounds
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Lattice enthalpy, the energy to break down one mole of an ionic solid into gaseous ions, is determined by the formula: ∆HΘLE = ∆HΘf - [ (∆HΘat (______)) + (∆HΘat (______)) + IE1 + EA1 ].
cation
anion
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Born-Haber cycle application
Applies Hess's Law to relate lattice enthalpy to other enthalpy changes.
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Enthalpy values in lattice enthalpy calculation
Includes formation, atomization, ionization, and electron affinity enthalpies.
