[positiveion]

Edit: sorry, the poll thing was an error

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.

[positiveion]

an additional problem that i tried:



were my arrows correct? :S idk it was a wild attempt and i am really confused

[biosynthesis]

Hi,

Just wanted to comment that not every energetics questions require Hess's Law to solve. There is another easier way to do it.

Much easier.

Anyway, to answer your question. your delta H are not properly position in the equation.

it's not H1 = H2-H2.. Look carefully at your arrows again.

[Astatine]

If I'm not wrong, two of your arrows are wrong.

Look at the data given properly. Use the equation to help you decide which way the arrow should be facing.
Reference to your post, it should be delta H3 - delta H2.