Reversible Work and Maximum Work

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Julia Go 2L
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Reversible Work and Maximum Work

Why does reversible expansion do more work than an irreversible expansion?

Sierra Cheslick 2B
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Re: Reversible Work and Maximum Work

Reversible expansion is slower, and therefore more work is done since less energy is lost as heat.

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Re: Reversible Work and Maximum Work

The expansion for a reversible system is done infinitely slowly and less heat is released to the surroundings resulting in more work done. You can better understand this process by viewing the pressure volume graphs for the two types of systems. The area under the curves shows you the work done by the systems. Clearly you can see which one does more work using those graphs.

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Re: Reversible Work and Maximum Work

From my knowledge, reversible reactions happen simultaneously, whereas an irreversible goes in steps. For this reason, say we were to calculate the area under the curve of the two reactions, the work is greater in a reversible reaction. The graph of a reversible is a curve (which has more area under) while the irreversible, because it happens in steps, tends to be just a rectangle of sorts. To illustrate this, imagine decreasing pressure first, which would cover no area, the line would remain stagnant, but the point would just drop.

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Re: Reversible Work and Maximum Work

When a gas expands reversibly, the external pressure is matched to the pressure of the gas at every stage of the expansion. Thus, the steps that correspond to the increase in volume are infinitesimal, and thus achieve maximum area under the curve. This results in the maximum work.

Ray Guo 4C
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Re: Reversible Work and Maximum Work

Madeline Motamedi 4I wrote:The expansion for a reversible system is done infinitely slowly and less heat is released to the surroundings resulting in more work done. You can better understand this process by viewing the pressure volume graphs for the two types of systems. The area under the curves shows you the work done by the systems. Clearly you can see which one does more work using those graphs.

The graph does make sense, but why does a reversible expansion lose less heat?