Calculate the lattice energy in kJ/mol for CaCl2 from the following information: Energy needed to vaporize one mole of Ca(s) is 192kJ. For calcium the first ionization energy is 589.5kJ/mol and the second ionization energy is 1146kJ/mol.
The electron affinity of Cl is -348kJ/mol.
The bond energy of Cl2 is 242.6kJ/mol of Cl-Cl bonds.
The standard heat of formation of CaCl2 is -795kJ/mol
The answer I found is -2269.1 kj/mol
Is this right or did I make a mistake
To calculate the lattice energy of CaCl2, we need to consider several factors including the formation of CaCl2 from its elements, the ionization energies of calcium, the electron affinity of chlorine, and the bond energy of Cl2.
The lattice energy (ΔH_lattice) can be calculated using the following equation:
ΔH_lattice = ΔH_formation + IE + EA - bond energy
1. ΔH_formation: The standard heat of formation of CaCl2 (-795 kJ/mol) indicates the heat released or absorbed when one mole of CaCl2 is formed from its elements. In this case, since the value is negative, it means the reaction is exothermic, and energy is released.
2. IE: The ionization energy (IE) refers to the energy required to remove electrons from an atom or ion. Calcium has two ionization energies since two electrons need to be removed to form Ca2+ ions. The first ionization energy of calcium (589.5 kJ/mol) represents the energy required to remove one electron from a neutral calcium atom to form Ca+. The second ionization energy (1146 kJ/mol) represents the energy required to remove a second electron from a Ca+ ion to form Ca2+.
3. EA: The electron affinity (EA) of chlorine (-348 kJ/mol) represents the energy released when a chlorine atom gains an electron to form Cl- ion.
4. Bond energy: The bond energy of Cl2 (242.6 kJ/mol) represents the energy required to break one mole of Cl-Cl bonds.
Now, let's substitute these values into the equation:
ΔH_lattice = -795 kJ/mol + 589.5 kJ/mol + 1146 kJ/mol + (-348 kJ/mol) - 242.6 kJ/mol
Calculating these values gives us:
ΔH_lattice = -649.1 kJ/mol
Therefore, the lattice energy of CaCl2 is approximately -649.1 kJ/mol.