Reversible and Irreversible Processes


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Reversible and Irreversible Processes

Postby Stephanie_Thai_2C » Sat Jan 14, 2017 11:55 pm

Can someone clarify the importance of reversible processes in chemistry and work? I understand the difference of reversible and irreversible processes in that the former can be reversed by a infinitely small change in a variable but I can't see the connection to its significance in work.

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Re: Reversible and Irreversible Processes

Postby Esther_Choe_1K » Sun Jan 15, 2017 11:29 am

I have the same question specifically regarding why the work a system can do is greatest in a reversible process..

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Re: Reversible and Irreversible Processes

Postby Aishwarya_Natarajan_2F » Sun Jan 15, 2017 11:30 am

Reversible processes can be reversed by an infinitely small change in a variable while an irreversible process doesn't. One of the applications of these two is taking the example of a piston, when can reverse directions in a reversible process with small changes in pressure, and this doesn't happen in the case of a reversible process.

If we look at Boyle's law, as volume increases, pressure decreases when the gas expands. As a result, if we want to achieve a reversible expansion, we have to reduce external pressure as well because the internal pressure of the gas is falling as it expands. There is a box on pg 265 explaining the derivations of the equation, but this is the idea behind it.

In a reversible expansion, external pressure is reduced to match internal pressure. In an irreversible expansion, we don't change external pressure and because of this some of the potential of the system to do work is lost with the opposing pressure externally. In reversible expansions, since internal pressure = external pressure, the system has the potential for the maximum amount of work. Example 8.2 does a pretty good job illustrating how to use the two equations.

I hope this answered your question!

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