Born-Haber Cycle for Calcium Chloride

The standard enthalpy of formation of calcium chloride is -795kJmol^-1,the equation for the reaction is:Ca(s) + Cl₂(g) → CaCl₂(s)The definition states that the -795kJ is the enthalpy for 1 mole of calcium chloride. The definition of the enthalpy of atomisation is for the formation of 1 mole of calcium atoms and 1 mole of chlorine atoms but we need to form 2 Cl(g)so the enthalpy change for the atomisation will be 2 x (+121) kJ mol^-1 for chlorine. The definition of the enthalpy of atomisation is for the formation of 1 mole of calcium atoms so we can use the standard enthalpy of atomisation which is +178 kJmol^-1 as it is. The next step is to ionise the calcium. The equation for the first ionisation energy is:Ca(g) → Ca⁺(g) + e^-The first ionisation energy for calcium is +590 kJ per mole. The calcium ion has a +2 charge so a second ionisation energy (+1145 kJ per mole) is needed.Ca⁺(g) → Ca²⁺(g) + e^-Mass and charge are conserved for each step. We now have 2x the electron affinity for chlorine.2Cl(g) + 2e^- → 2Cl^-(g)The cycle is completed with the Lattice (formation) enthalpyCa²⁺(g) + 2Cl^-(g) → CaCl₂ (s)