[eigen]

Hi, all!  First post!

Can anyone walk me through how to solve this problem using Hess's Law?  I simply cannot wrap my head around it.  I've written it out for you below.

Thanks! 

[eigen]

Oh well, I figured it out.  If anyone else is interested, here's the solution:

Reverse (3):


Add it to (4):


Cancel and subtract from each side:


Double it:


Add it to (2):


Cancel the and combine the two :


Now the final equation matches the original equation, therefore the enthalpy change for the reaction is .

Edit: fixed LaTeX.