Gibb's Energy and Work

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Leah Savage 2F
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Joined: Fri Sep 29, 2017 6:06 am

Gibb's Energy and Work

Postby Leah Savage 2F » Tue Feb 13, 2018 10:42 pm

Is Gibb's free energy only for nonexpansion work?
What is the relationship between gibb's free energy and work? what kind of system is w=-P(deltaV) for if it's not for reversible/irreversible processes? Irreversible/reversible processes do expansion work, right?

Michelle Chernyak 1J
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Re: Gibb's Energy and Work

Postby Michelle Chernyak 1J » Wed Feb 14, 2018 10:07 am

w=-PdeltaV applies to the work done in a irreversible expansion and yes both irreversible and reversible processes do expansion work, there are just two different equations used to solve for w.

Austin Ho 1E
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Re: Gibb's Energy and Work

Postby Austin Ho 1E » Wed Feb 14, 2018 10:09 am

I don't think Gibb's Free Energy is only for non-expansion work. Both systems with irreversible and reversible processes can do expansion work. In theory, ΔG=wmax, or the maximum amount of work that can be done is ΔG.

In an irreversible expansion, w=-PΔV; pressure is constant while volume changes. This is because we suddenly change pressure, and wait for volume to shift accordingly.

In a reversible expansion, w=-nRTln(V2/V1); temperature is constant while pressure and volume change simultaneously. This is because external pressure is slowly being adjusted to make the changes infinitesimally small, and thus reversible.

Hope this helps.

Susie Lee 2I
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Re: Gibb's Energy and Work

Postby Susie Lee 2I » Thu Mar 01, 2018 10:18 am

Gibbs Free Energy measures the useful work obtainable from a thermodynamic system at a constant temperature and pressure.

Rishi Khettry 1L
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Re: Gibb's Energy and Work

Postby Rishi Khettry 1L » Sat Mar 17, 2018 1:01 am

Gibbs free energy does not apply only to nonexpansion work

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