Determining if a reaction is endothermic or exothermic

Moderators: Chem_Mod, Chem_Admin

Tiffany Tam
Posts: 11
Joined: Fri Sep 25, 2015 3:00 am

Determining if a reaction is endothermic or exothermic

Postby Tiffany Tam » Mon Nov 30, 2015 11:31 pm

In question 6 part C of the first practice final in the course reader. How do you determine whether the reaction is exothermic or endothermic if there are no H values given? Is it based on the lewis structure?

Ronald Yang 2F
Posts: 86
Joined: Fri Sep 25, 2015 3:00 am

Re: Determining if a reaction is endothermic or exothermic

Postby Ronald Yang 2F » Tue Dec 01, 2015 12:11 am

If no H values are given, the best way is to look at what's happening in the reaction. For the reaction N2O4 <-> 2 NO2, a bond between the two nitrogens is broken apart. Since breaking a bond requires energy, this reaction must be endothermic. I'm now looking at the course reader, and this is pretty much what is in the explanation. I guess if you didn't initially know that a bond is being broken, it would be best to draw out the lewis structures, compare the product(s) with the reactant(s), and determining what is happening in the reaction.


Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 2 guests