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# Free energy and cell potential

Explore the relationship between cell potential and free energy in voltaic cells. Understand how to calculate Faraday's constant and use it to determine the standard change in free energy. Discover the conditions for standard cell potential and how it links to spontaneous redox reactions.
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## Want to join the conversation?

• why is Gibbs free energy negative for spontaneous reactions?
• The underlying reason for this is merely that of convention; in thermodynamics, negative values represent energy RELEASED by a system, heat RELEASED by a system, or work DONE by a system. Conversely, positive values represent energy ABSORBED by a system, heat ABSORBED by a system, or work done UNTO a system.

Taking just one step back by taking a look at the equation for Gibbs free energy, we see that G = H - TS. If H, or enthalpy, is negative, then we know that the reaction RELEASES heat energy, which contributes to spontaneity. Additionally, if the S, or entropy, term is positive, then we know that the reaction is associated with an increase in entropy, which contributes to spontaneity. This is why the entropy term is subtracted from the enthalpy term; a larger (more positive) entropy should make the Gibbs free energy more negative. :)