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Dejan_3900
#1 Posted : Wednesday, July 08, 2020 10:24:08 PM
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In what situation would we see enthalpy being positive and the overall process being exothermic?
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INSTR_Molly_59
#2 Posted : Saturday, July 11, 2020 5:53:41 PM
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Are you talking about Gibbs free energy, and a reaction being exergonic (spontaneous)?

In no case, would a reaction ever be exothermic (heat releasing) and have a positive enthalpy (dH). Exothermic itself dictates a negative dH (d = delta, the triangle symbol).

Exergonic however, refers to the calculation of Gibbs free energy, which incorporates the temperature, and entropy, as well, to calculate the absorbance or release of energy of the system.

Gibbs free energy equation states: dG = dH - TdS

So if you are looking for a reaction that is exergonic, you are looking for a negative dG. To have a negative dG with a positive enthalpy, your TdS MUST be even more negative. So therefore, you require -TdS > dH for your reaction to be exergonic.

Hope this helps! If you need more assistance, please reply below.

Cheers, and happy studying! :)
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