Bond Enthalpy and Enthalpy of Formation

Moderators: Chem_Mod, Chem_Admin

Brian Huynh 3D
Posts: 20
Joined: Wed Sep 21, 2016 2:58 pm

Bond Enthalpy and Enthalpy of Formation

Postby Brian Huynh 3D » Thu Jan 12, 2017 9:55 am

Professor Lavelle covered in class that the Enthalpy of formation of O2 is 0. Are there any other exceptions like this?

Maggie Bui 1H
Posts: 35
Joined: Fri Jul 22, 2016 3:00 am
Been upvoted: 1 time

Re: Bond Enthalpy and Enthalpy of Formation

Postby Maggie Bui 1H » Thu Jan 12, 2017 10:18 am

It's not so much that O2 is an exception as it is that the standard enthalpy of formation of an element in its most stable form is 0 (this definition is found on page 294 of the book). I think this makes more sense if you think about the "reaction" you'd need to form these elements. You could write down a reaction, but since the reactants of the reaction would be the constituent elements in their most stable form, the reactants and products of a reaction making an element in its most stable form would be the same.

Celina N 2H
Posts: 11
Joined: Wed Sep 21, 2016 2:58 pm
Been upvoted: 1 time

Re: Bond Enthalpy and Enthalpy of Formation

Postby Celina N 2H » Thu Jan 12, 2017 3:13 pm

The enthalpy of formation of oxygen (O2) is 0 because O2 is the element oxygen in its most stable state. Therefore, elements in their most stable states (e.g., H2 for hydrogen, F2 for fluorine, C for carbon, etc.) all have enthalpy of formation equal to 0. In all other less stable forms, enthalpy of formation will not equal 0.

Jocelyn_Limas_2G
Posts: 12
Joined: Fri Jul 15, 2016 3:00 am

Re: Bond Enthalpy and Enthalpy of Formation

Postby Jocelyn_Limas_2G » Thu Jan 12, 2017 11:39 pm

If the standard enthalpy of formation is not found on the tables given, is it then safe to assume that it equals 0?

Trisha Agarwal 1O
Posts: 11
Joined: Wed Sep 21, 2016 2:56 pm

Re: Bond Enthalpy and Enthalpy of Formation

Postby Trisha Agarwal 1O » Fri Jan 13, 2017 10:06 am

If it's not on the table it is most likely an element that is in its standard state, so I it would be 0.


Return to “Phase Changes & Related Calculations”

Who is online

Users browsing this forum: No registered users and 1 guest