The reaction of electropositive metals with electronegative nonmetals produces ionic compounds. Let us look into Born Haber cycle and some chemical reactions in detail to explain the methodology of Born Haber Cycle. Also, it further enables us to understand the overall reaction process through a series of steps. This method helps us in describing the formation of ionic compounds from different elements. Observe and analyze energies in a reaction. The method also exhibits several properties such as electron affinity, ionization energy, sublimation energy, the heat of formation and dissociation energy. It is primarily used to calculate the lattice energy which is a measure of the strength of ionic bonds that exist in an ionic compound involved in a chemical reaction. This methodology was introduced in the year 1919 by German scientists Fritz Haber and Max Born. It further enables us to understand the overall reaction process through a series of steps involved in it. This process describes the formation of ionic compounds from different elements. Chlorine ions are large and hence are easily polarised.Born Haber process or more commonly known as Born Haber cycle is a method in use that lets us observe and analyze energies in a reaction. Magnesium ions can closely approach the electron density of the negative chloride ions and polarise their charge. Smaller, positively charged ions are more polarising. This is due to magnesium ions being relatively small with a highly positive charge of +2. This is evidence that there are stronger bonding forces present than purely ionic. This is evidence of covalent character in the bonding within ionic lattices.Įxample: Magnesium Chloride Thermodynamic – Calculations involving Born-Haber Cyclesįor MgCl2, the experimental lattice enthalpy of formation is more exothermic. The experimentally calculated value is more exothermic than the theoretical value.This is evidence that many ionic compounds in fact show some degree of covalent character. The perfect ionic model is entirely theoretical, and it is seen that there is deviation from experimentally calculated values of lattice enthalpy using a Born-Haber cycle: The experimentally calculated value is more exothermic than the theoretical value. There is no covalent character in the bonds, it is purely ionic.The attractions are purely electrostatic.All ions have an even charge distribution.This is because many ionic compounds are not purely ionic but show some covalent character. Lattice enthalpies from Born-Haber cycles are sometimes higher than the values calculated from assumptions based on the perfect ionic model. Therefore ΔfH = -787kJmol-1 so the lattice enthalpy of sodium chloride is -787 kJ mol-1.Ĭomparing Lattice Enthalpies from Born-Haber Cycles To work out the value of ΔHf we are going to use the other values in the cycle. ΔHf represents the lattice enthalpy of formation of sodium chloride. Thermodynamic – Calculations involving Born-Haber Cycles Let’s revisit the Born-Haber Cycle for NaCl we looked at in the previous Chapter. If you have the values for all of the stages but one, you can work out the value of the unknown stage, using the principle of Hess’s Law. This process is made up of different stages, each of which corresponds to a different enthalpy change. Hess’s Law states that the total enthalpy change of a chemical reaction is the same independent of the route taken from products to reactants.īorn-Haber cycles illustrate the relationships between the different enthalpy changes involved in the formation of an ionic compound. This is possible due to the principle of Hess’s Law. Thermodynamic - Calculations involving Born-Haber Cycles (A-Level Chemistry) Calculations involving Born-Haber Cycles Calculations with Born-Haber Cycles Key TermsĪ Born-Haber cycle is a thermochemical cycle that includes every enthalpy change that is involved in an ionic compound formation process. Chemistry Teacher Resource Edexcel | AQA | OCR.Biology Teacher Resource Edexcel | AQA | OCR | CIE.Chemistry Flashcards Edexcel | AQA | OCR | CIE.Biology Flashcards Edexcel | AQA | OCR | CIE.Chemistry Textbook Edexcel | AQA | OCR | CIE.Biology Textbook Edexcel | AQA | OCR | CIE.Physics Weekly Classes Edexcel | AQA | OCR | CIE.Chemistry Weekly Classes Edexcel | AQA | OCR | CIE.Biology Weekly Classes Edexcel | AQA | OCR | CIE.GCSE Physics Flashcards Edexcel | AQA | OCR | CIE.
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