Question

Calculate the lattice energy 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 CI-Cl bonds. The standard heat of formation of CaCl2 is -795kJ/mol. (include the sign and your numerical answer, do not include units, do not use scientific notation, and round your answer to 1 decimal point)

Answer 1

Answer:

The correct answer is -2268.5 KJ/mol

Explanation:

Find attached the diagram for Born-Haber cycle. The solid calcium (Ca (s)) can be first sublimated into its atoms in gaseous phase and then the atoms are ionizated two times to give the cations in gaseous phase. The gaseous chlorine (Cl₂(g)) is first dissociated into its gaseous ions and then the atoms are ionizated to give anions in gaseous state. The lattice energy (LE) is the energy involved in the formation of the solid CaCl₂ from the elementary ions in gaseous state.

From Born-Haber cycle we have:

ΔHºf= ΔHvap + IE₁ + IE₂ + BE + 2 x EA + LE

⇒ LE= ΔHºf - ΔHvap - IE₁ - IE₂ - BE - (2 x EA)

   LE= -795 KJ/mol - 192 KJ/mol - 589 KJ/mol - 1146 KJ/mol - 242 KJ/mol - (2 x (-348 KJ/mol))

LE= -2268.5 KJ/mol