[gvsu88]

The major source of aluminum in the world is bauxite (mostly aluminum oxide). The metal can be purified through thermal decomposition to form aluminum and oxygen. How many grams of aluminum can be produced when 7681.1 kJ of heat is applied to the ore?

I have the equation
2Al2O3 --> 4Al + 3O2

Then I found enthalpy of reaction, 0 - (2 x -1675.7) = 3351.4kJ

then I'm trying to do the rest but it keeps coming out wrong. I know that I need to compare mole - mole and everything but I'm having a hard time with this problem specifically for some reason. So I'd appreciate some help. Thanks

[Borek]

Then I found enthalpy of reaction, 0 - (2 x -1675.7) = 3351.4kJ

kJ per what? Enthalpy of the reaction is always given as amount of energy produced (or consumed) per amount of substance (produced or consumed), or per so called "mole of reaction". You listed here some numbers, but it is hard to say what they do represent.

[JustinCh3m]

Well, 4 moles of Al are being produced when an energy of 3351.4kJ is consumed.  That being said, use dimensional analysis to find how many moles (and thus grams) of Al are formed when 7681.1kJ of heat are applied.  This should point you in the right direction...