Calculate the lattice energy of Calcium Chloride (CaCl2) using Born-Haber cycle and Hess's law, given that the following information:- Dissociation energy of Cl2 molecule is 243 kJ/mol- First ionization energy of Ca atom is 590 kJ/mol- Second ionization energy of Ca atom is 1145 kJ/mol- Electron affinity of Cl atom is -348 kJ/mol- Heat of sublimation of Ca metal is 178 kJ/mol- Bond energy of Cl-Cl molecule is 242 kJ/mol

Question

Calculate the lattice energy of Calcium Chloride (CaCl2) using Born-Haber cycle and Hess's law, given that the following information:- Dissociation energy of Cl2 molecule is 243 kJ/mol- First ionization energy of Ca atom is 590 kJ/mol- Second ionization energy of Ca atom is 1145 kJ/mol- Electron affinity of Cl atom is -348 kJ/mol- Heat of sublimation of Ca metal

Answer 1

To calculate the lattice energy of CaCl2 using the Born-Haber cycle and Hess's law, we need to consider the following steps:1. Sublimation of Ca metal2. Ionization of Ca atom3. Dissociation of Cl2 molecule4. Electron affinity of Cl atom5. Formation of CaCl2 latticeStep 1: Sublimation of Ca metalHeat of sublimation of Ca = 178 kJ/molStep 2: Ionization of Ca atomFirst ionization energy of Ca = 590 kJ/molSecond ionization energy of Ca = 1145 kJ/molTotal ionization energy of Ca = 590 + 1145 = 1735 kJ/molStep 3: Dissociation of Cl2 moleculeBond energy of Cl-Cl molecule = 242 kJ/mol We will use the given value of 242 kJ/mol instead of 243 kJ/mol, as it is more accurate for this calculation Step 4: Electron affinity of Cl atomElectron affinity of Cl = -348 kJ/molSince there are two Cl atoms in CaCl2, the total electron affinity = 2 *  -348  = -696 kJ/molStep 5: Formation of CaCl2 latticeLet the lattice energy be L.Now, we can apply Hess's law to find the lattice energy:Hf  CaCl2  = Sublimation energy + Ionization energy + Dissociation energy + Electron affinity + Lattice energyWe know that the enthalpy of formation  Hf  of CaCl2 is -795 kJ/mol. Therefore:-795 kJ/mol = 178 kJ/mol + 1735 kJ/mol + 242 kJ/mol - 696 kJ/mol + LNow, we can solve for L:L = -795 - 178 - 1735 - 242 + 696L = -2254 kJ/molSo, the lattice energy of CaCl2 is -2254 kJ/mol.