Help with Hess' Law Application

[masochist]

I'm having a lot of trouble understanding this and I've been trying to figure it out for days.

I completely understand Hess' law I just have no idea how to apply it in various scenarios. How do I draw the triangle? How do I split up the equation? When and where does the arrow point up or down?

So far I understand that there are 4 types of things that we've learned about that we need to apply the Hess' Law triangle to:

- standard enthalpy of formation

- standard enthalpy of combustion

- standard enthalpy of atomisation

- bond enthalpies

but i've watched so many videos/read so much stuff on the subject most of which i understand while i'm watching it but i don't know WHY and i don't know HOW.

thank you very much.

[Sandwich]

I recall being in your exact position -- I understood the triangle but for some reason could never figure out how to draw one and then use it to solve something!!

You can actually use a non-triangle based method using equations instead, which I personally much, much, much preferred. I mean, I hate maths and equations as a rule, but these are very simple and considerably more comprehensible than triangles. If I recall correctly I learned how to do them from IB Chem.com (http://ibchem.com/IB/ibnotes/brief/ene-hl.htm#ex1). I think there may also have been an example doing it this way in our textbook (the Neuss one), but I'm not 100%. Either way, my advice is scrap the triangle! After working out this method, it never failed me P:

[masochist]

Thank you very much!