What is the lattice energy of calcium chloride?

Question

The heat of solution of calcium chloride CaCl2 is –82.8 kJ/mol, and the combined heats
of hydration of 1 mole of gaseous calcium ions and 2 mole of gaseous chloride ions is
–2327 kJ. What is the lattice energy of calcium chloride?

Fern · Answer

(1) Heat of solution:   CaCl2(s)  ==  Ca2+(aq)   +  2Cl-(aq)    -82.8 kJ
(2) Hydration Energy:   Ca2+(g)   +  2Cl-(g)  ===   Ca2+(aq)  +  2Cl-(aq)     -2327 kJ

Reverse (1) and change sign: Then add the following equations:  
                              Ca2+(aq)   +  2Cl-(aq)    ==  CaCl2(s)      +82.8  kJ  
                             Ca2+(g)   +  2Cl-(g)  ===   Ca2+(aq)  +  2Cl-(aq)     -2327 kJ
=========================================================
Lattice Energy    Ca2+(g)    +  2Cl-(g)  ==  CaCl2(s)    -2244.2 kJ

What is the lattice energy of calcium chloride?

1 Answer