Irreversible Expansion Explained

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

Leonardo Le Merle 1D
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Joined: Wed Feb 27, 2019 12:16 am

Irreversible Expansion Explained

Can someone clarify what exactly an irreversible expansion would look like? As in explain it with an analogy; something besides the piston one.

Osvaldo SanchezF -1H
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Joined: Wed Sep 18, 2019 12:21 am

Re: Irreversible Expansion Explained

Instead of a piston you can think of a ballon where you do work on it by blowing air into it. Initially the ballon has a fixed volume and when you blow air the volume will increase and stay at a fixed amount (at least when you tie the not. So then you can apply the irreversible equation for work w=pdeltaV if need be.

Hui Qiao Wu 1I
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Joined: Fri Aug 30, 2019 12:16 am

Re: Irreversible Expansion Explained

Adding on to the balloon analogy, for me, reversible is slowly blowing air into the balloon so it "expands" or releasing air so it "compresses;" it can go both ways. Irreversible, on the other hand, is blowing the balloon so fast that it pops, so there is no way of going back.

Lara Kristine Bacasen 1L
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Re: Irreversible Expansion Explained

For me I remember the graphs he showed us in lecture for the reversible and irreversible reactions. For the reversible reactions the curve is smooth while the irreversible reaction is like a step. You can roll a ball up and down the curve but if you try to roll a ball on the step its can't go back up and stays on the level that it is on.

Kristina Rizo 2K
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Re: Irreversible Expansion Explained

This is kind of irrelevant to the question but will the question always say if it is reversible or irreversible? Or is there another way we will know which equation to use?

Juliet Stephenson 4E
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Joined: Wed Sep 18, 2019 12:21 am

Re: Irreversible Expansion Explained

Kristina Rizo 2K wrote:This is kind of irrelevant to the question but will the question always say if it is reversible or irreversible? Or is there another way we will know which equation to use?

I am pretty sure the question will always say whether the expansion is reversible or irreversible. I am not aware of a way we could figure it out if it weren't provided.

Noe BM 1J
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Joined: Sat Sep 07, 2019 12:17 am

Re: Irreversible Expansion Explained

I was about to ask the same question since homework problems specify whether it's reversible or irreversible, so I didn't know if we have to know based on the given information.

Juliet Stephenson 4E wrote:
Kristina Rizo 2K wrote:This is kind of irrelevant to the question but will the question always say if it is reversible or irreversible? Or is there another way we will know which equation to use?

I am pretty sure the question will always say whether the expansion is reversible or irreversible. I am not aware of a way we could figure it out if it weren't provided.

Areena H 2K
Posts: 81
Joined: Wed Dec 05, 2018 12:18 am

Re: Irreversible Expansion Explained

Irreversible would be pumping air into a balloon or gas bump and it happens suddenly while reversible would be slowly adding air into it gradually.