Units for Gibbs Free Energy


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Helena Vervaet 1N
Posts: 26
Joined: Wed Sep 21, 2016 2:59 pm

Units for Gibbs Free Energy

Postby Helena Vervaet 1N » Tue Feb 14, 2017 3:50 pm

Is there a difference between using kJ vs. kJ/mol when labelling Gibbs Free Energy? I've run across a few problems where you must multiply each molecule's standard value of formation by its number of moles in the reaction, but sometimes the units for the free energy of the reaction are written differently. I would think if you are multiplying everything by the number of moles, you would be cancelling those out in each individual calculation and be left with just kJ (Like in problem #8 on the 2015 midterm). In other cases, they leave the units as kJ/mol. Are both units correct for the Gibbs free energy of the reaction?

Chem_Mod
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Re: Units for Gibbs Free Energy

Postby Chem_Mod » Tue Feb 14, 2017 9:54 pm

If you are given the number of moles, do the multiplication.

Luke Bricca 1H
Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

Re: Units for Gibbs Free Energy

Postby Luke Bricca 1H » Thu Feb 15, 2018 7:52 am

Usually Gibbs Free Energy is given in kJ/mol, but you can multiply out the moles and just have kJ. By multiplying the Gibbs Free Energy by the number of moles, you're cancelling them in the denominator.

melissa carey 1f
Posts: 53
Joined: Fri Sep 29, 2017 7:06 am

Re: Units for Gibbs Free Energy

Postby melissa carey 1f » Thu Feb 15, 2018 9:11 am

When a problem asks for Gibbs Free energy in "kJ" does this mean kJ/mol or just kJ?

Humza_Khan_2J
Posts: 56
Joined: Thu Jul 13, 2017 3:00 am

Re: Units for Gibbs Free Energy

Postby Humza_Khan_2J » Thu Feb 15, 2018 9:58 am

Dr. Lavelle said he would be relatively lenient on accepting either kJ or kJ/mol. This is because, given a particular reaction, the delta G is generally the delta G for the reaction as a whole, as written. This could be said as "per mole equivalent" of the reaction.


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