Gibbs Free Energy and Electrochemistry

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Daniel Dobrin 2F
Posts: 12
Joined: Sat Jul 09, 2016 3:00 am

Gibbs Free Energy and Electrochemistry

Postby Daniel Dobrin 2F » Fri Feb 03, 2017 1:46 pm

What is the relation between Gibbs free energy and electrochem? I don't understand why we can calculate G in this section.

Laura Rabichow 1J
Posts: 29
Joined: Fri Jun 17, 2016 11:28 am

Re: Gibbs Free Energy and Electrochemistry

Postby Laura Rabichow 1J » Fri Feb 03, 2017 2:01 pm

Page 49 of the course reader may explain this better, but basically the maximum work (wmax) is related to the cell potential E by E = -w/charge. Rearranging gives you -charge x E = w. Faraday's constant gives the charge of 1 mol of electrons and multiplying by the number of moles of electrons transferred gives you the charge (charge = nF). This gives the equation -nFE = w = deltaG.

Simon Kapler 3I
Posts: 15
Joined: Mon Sep 26, 2016 3:01 am

Re: Gibbs Free Energy and Electrochemistry

Postby Simon Kapler 3I » Fri Feb 03, 2017 2:07 pm

In order for an electrochemical reaction to occur/be useful, it has to occur spontaneously, right? Powerful batteries have a super negative deltaG, which is what allows them to do so much useful work. Electricity naturally flows from high to low electric potential (E) in a similar manner to heat flowing from a region of high to low temperature. For example, a battery using two substances with a relatively small difference in E (low voltage) will not generate much current (electrical flow), and therefore can do less work than a battery with a larger deltaE. In this way, G and E are related: G tells you whether the electricity will flow in the direction you want it to on its own, and E tells you how much the electricity "wants" to flow from one substance to another.

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