when to add all delta H, when to subtract delta H.

[wkawk2416]

---

Members do not see this ad.

some problem says i have to subtract reactant delta H from product delta H. ex. product delta H - reactant delta H

where other problem, we can just add up and get the answer.

i am confused.

 

[wkawk2416]

yeah, i understand that.

but sometimes, the question itself is oriented like

it will give you a correct answer when all hess laws are added up.

but sometimes, like question # 121 on destoyer.

you have add all up to get the right answer.