standard reaction enthalpy

Moderators: Chem_Mod, Chem_Admin

Katie Bart 1I
Posts: 104
Joined: Sat Aug 24, 2019 12:16 am

standard reaction enthalpy

Postby Katie Bart 1I » Tue Feb 04, 2020 10:00 pm

When you find the standard reaction enthalpy for a reaction, is the value in units of kJ or kJ/mol? I've seen both used in the textbook.

Skyllar Kuppinger 1F
Posts: 52
Joined: Thu Jul 25, 2019 12:16 am

Re: standard reaction enthalpy

Postby Skyllar Kuppinger 1F » Tue Feb 04, 2020 10:07 pm

If it asks you for the standard enthalpy of a reaction then it will be in kj bc you can't really have moles of a reaction. If it's the standard enthalpy of FORMATION then it is kj/mol bc that is the enthalpy change that occurs when one mole of that molecule is formed.

Caitlyn Tran 2E
Posts: 100
Joined: Fri Aug 09, 2019 12:15 am

Re: standard reaction enthalpy

Postby Caitlyn Tran 2E » Tue Feb 04, 2020 10:09 pm

If it is standard reaction enthalpy, it may say kJ or kJ/mol, but it is implied that the standard reaction enthalpy given is for one "mole" of reaction. You can't really have a mole of a reaction, so this just means that the given standard reaction enthalpy is the enthalpy proportional to the moles of each compound given. If you multiply the reaction by a coefficient of 2, you will have to multiply the standard reaction enthalpy by 2 as well. It follows the same rules as used in Hess's Law. Hope this helps!

IScarvie 1E
Posts: 66
Joined: Sat Aug 17, 2019 12:16 am

Re: standard reaction enthalpy

Postby IScarvie 1E » Wed Feb 05, 2020 6:27 pm

Both are acceptable, however Standard Enthalpy of Formation is required to be in kJ/mol.


Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

Who is online

Users browsing this forum: No registered users and 2 guests