Problem: The standard heat of formation of CaBr2 is -675 kJ/mol. The first ionization energy of Ca is 590 kJ/mol and its second ionization energy is 1145 kJ/mol. The heat of sublimation of Ca is 178 kJ/mol. The bond energy of Br2 is 193 kJ/mol, the heat of vaporization of Br2 (l) is 31 kJ/mol, and the electron affinity of Br is -325 kJ/mol.Calculate the lattice energy of CaBr2.

FREE Expert Solution

We’re being asked to calculate the lattice energy of calcium bromide (CaBr2)


Recall that lattice energy is the energy required to combine two gaseous ions into a solid ionic compound:


Mx+(g) + Ny–(g)  MyNx(s)


To calculate for lattice energy, we need to do the Born-Haber cycle for CaBr2


We start with the corresponding formation equation for CaBr2:

Ca(s) + Br2(g)  CaBr2(s), ΔH˚f


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Problem Details

The standard heat of formation of CaBr2 is -675 kJ/mol. The first ionization energy of Ca is 590 kJ/mol and its second ionization energy is 1145 kJ/mol. The heat of sublimation of Ca is 178 kJ/mol. The bond energy of Br2 is 193 kJ/mol, the heat of vaporization of Br2 (l) is 31 kJ/mol, and the electron affinity of Br is -325 kJ/mol.

Calculate the lattice energy of CaBr2.

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What scientific concept do you need to know in order to solve this problem?

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