How do I solve questions involving lots of theory and no calculations?

[airbusman]

I'm in a grade 12 university level chem class right now, and I'm getting a 72. I realized just today that the reason why I'm doing so poorly is because I'm good at calculations, but not questions that involve even more thinking.

For instance, one question gave us some information about aluminum reacting with oxygen to form aluminum oxide, and it asked why the enthalpy of reaction for this reaction is not detectable, even though the reaction is exothermic and it has a large enthalpy change.

How would you approach questions like this?

 

[Borek]

one question gave us some information about aluminum reacting with oxygen to form aluminum oxide, and it asked why the enthalpy of reaction for this reaction is not detectable

Actually I have no idea what the question is about, can you post a complete wording?

 

[airbusman]

Here it is:

"Aluminum is a reactive, self-protecting metal used to make doors, windows, and siding for houses. It reacts quickly with O₂ to form an impervious coating of aluminum oxide, that prevents O₂ from reacting any further with the aluminum. This reaction is unnoticeable even though the reaction shown below indicates a large enthalpy change. Why is the enthalpy of reaction not detectable?"

4Al(s) + 3O₂(g) → 2Al₂O₃(s) +33351.4 kJ

 

[Borek]

How thick is the oxide layer?

 

[DrDu]

You should show your teacher some burning aluminium powder.