Calculate overall energy changes (in kilojoules per mole) for the fromation of MgF and MgF2 from their elements.
The following data are needed:
Eea for F = -328 Kj/mol
Ei1 for Mg = 737.7Kj/mol
Ei2 for Mg = 1450.7 Kj/mol
Heat of Sublimation for Mg = +147.7Kj/mol
Bond dissociation energy for F2 = 158 Kj/mol
Lattice energy for MgF2 = 2952 Kj/mol
Lattice ebergy for MgF = 930 Kj/mol (estimated)

Could you please walk me through solving this problem

Well, the way I do it is through a 'Born-Haber Cycle' for the reaction. Tell, me you know about this? I could better explain with one.

Quote:

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Originally Posted by Unknown008

Well, the way I do it is through a 'Born-Haber Cycle' for the reaction. Tell, me you know about this? I could better explain with one.

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Yes, we have touched on those. I am pretty sure I could understand.

Ok, have you drawn one?

You do surely understand that the steps to go through are:
1) Atomisation of Mg(s) to Mg(g)
2) Atomisation of 0.5F2(g) to F(g)
3) Ei1 of Mg (for MgF to be formed, you need Mg+ and F-) to Mg+
4) Eea of F to F-
5) Lattice energy of Mg+ and F-

1) up to 3) are endothermic, and 4) and 5) are exothermic. You should have put all the negative signs for the exothermic processes in your first post. Anyway, now, you can find the enthalpy of formation of MgF. Give it a try, I try to draw a born haber cycle.
4)

Attachment 25799

Post back your answer.

Now that the picture is here, it's sort of clearer to see. You can try with MgF2 if you want, and post the answer for this too.