Calculate the lattice energy (kJ/mol) of the hypothetical ionic compound MX from

Question

Calculate the lattice energy (kJ/mol) of the hypothetical ionic compound MX from the information given below.

IE1(M) = 538 kJ/mol
M(s) => M(g) ?Ho = 74.4 kJ/mol
?Hof(MX) = -169.7 kJ/mol
X2(g) => 2X(g) ?H = 157 kJ
EA (X) = -366 kJ/mol
IE1 (X) = 271 kJ/mol
Do not enter units with your answer.

The answer is -495. I don't even know where to start. I have no idea how to use the Ionization and energy and the Electron Affinity because we don't even know the compound!???

Explanation / Answer

Add together: [M(s) =>M(g) ?Ho]+(1/2)[X2(g) => 2X(g) ?H]+[IE1(M)]+[EA (X)] (the values added): 74.4+ (1/2)(157) + 538 +(-366) =324.9 kJ/mol now take ?Hof(MX) and subtract all of the things you added from it so you get: = -(169.7)-(324.9) = -494.6 = -495

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