Why do we care about ΔG






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Philip Lee 1L
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Why do we care about ΔG

Postby Philip Lee 1L » Fri Feb 15, 2019 3:18 pm

"The great importance of the introduction of Gibbs free energy is that, provided that the temperature and pressure are constant, the spontaneity of a process can be predicted solely in terms of the thermodynamic properties of the system" (7th Edition, pg 330)

Doesn't the equation ΔStot = ΔSsys - ΔH/T also satisfy "provided that the temperature and pressure are constant, the spontaneity of a process can be predicted solely in terms of the thermodynamic properties of the system"?
Why does the textbook emphasize that this is the reason why ΔG is so important?

Chem_Mod
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Re: Why do we care about ΔG

Postby Chem_Mod » Fri Feb 15, 2019 3:34 pm

The equation you proposed is the same as the ΔG = ΔH - T*ΔS equation we know and love, just in terms of different parameters. ΔG is related to ΔS, so yes, in a way, we can just use ΔS, but that is not always available to you. Plus, ΔG refers to the amount of free work available, whereas ΔS refers to the amount of disorder, so they measure different things, although they are related and reflect spontaneity.

Eunice Lee 1A
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Re: Why do we care about ΔG

Postby Eunice Lee 1A » Fri Feb 15, 2019 4:27 pm

You can figure out the spontaneity of a reaction simply from whether or not delta G is positive or negative.

Jake Gordon 1A
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Re: Why do we care about ΔG

Postby Jake Gordon 1A » Fri Feb 15, 2019 6:03 pm

It can help determine whether a reaction is thermodynamically favorable and if so, at what temperatures, also, delta G is the energy available to do work. If delta G decreases then heat is released and the energy can be used to do work I think this will come in to play in the future weeks


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