[gthomasset]

My chem teacher has thrown this question at our class with no direction or prior lesson

Lattice energy: 699 kJ/mol
first ionization energy of K = 418.7 kJ/mol
electron affinity of Cl = 349 kJ/mol
enthalpy of formation of KCl: -435.87 kJ/mol

what is the energy of sublimation for K, in kJ/mol?

we have no idea where to even begin on how to try to solve this.  My friends an I have been rereading the textbook for hours with no luck, so if someone could please explain howto solve this that would be amazing!

[Corribus]

First thing you need to do is define a balanced equation (or "reaction") for each of those processes, including the one you need to find. Then you can use a sort of Hess's Law formulation.

[gthomasset]

okay, then how do we do the hess's law part? bc its only for sublimation and we dont have a given mass. also there is a formula of delta m/delta t. is that correct?

[Corribus]

You don't need a mass, because kJ/mol is an intensive property.

Here's what I mean by coming up with a balanced equation for each process.

Energy of ionization of K is the process whereby a single, isolated atom of K (that is, in a gas) in its ground electronic state is completely ionized. The ionization energy, therefore, is:

K(g) K⁺(g) + e^-,  ΔE = 418.7 kJ mol^-1

http://en.wikipedia.org/wiki/Ionization_energy

The "gas" designation is usually just understood.

Can you define lattice energy, electron affinity, enthalpy of formation, and energy of sublimation similarly?

http://en.wikipedia.org/wiki/Lattice_energy
http://en.wikipedia.org/wiki/Electron_affinity
http://en.wikipedia.org/wiki/Standard_enthalpy_of_formation

You might find it helpful especially read the last article very carefully (hint, hint).

Actually, it looks to me like you are missing one important one, which is the bond enthalpy of Cl₂. Are you sure you haven't missed this one when writing up the problem here?