## Irreversible Work Chart

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

Mia Navarro 1D
Posts: 52
Joined: Fri Sep 29, 2017 7:04 am

### Irreversible Work Chart

Why does the pressure instantly drop at the beginning of the chart? In other words, what was the definition of the vertical brown line to the left?

Alvin Tran 2E
Posts: 39
Joined: Fri Sep 29, 2017 7:06 am

### Re: Irreversible Work Chart

The vertical brown line is the drop in the pressure. This was probably achieved by cooling at a constant volume (delta V = 0) so there is no work done.

Isita Tripathi 2E
Posts: 52
Joined: Sat Jul 22, 2017 3:00 am
Been upvoted: 1 time

### Re: Irreversible Work Chart

In lecture, Lavelle said to ignore the vertical brown line. I think it was drawn to compare the irreversible and reversible reactions. But, the external pressure was always constant, it didn't drop down all of a sudden.

Andy Nguyen 1A
Posts: 56
Joined: Thu Jul 27, 2017 3:00 am

### Re: Irreversible Work Chart

I think it was just used to show that a reversible reaction does more work than an irreversible reaction.

Alvin Tran 2E
Posts: 39
Joined: Fri Sep 29, 2017 7:06 am

### Re: Irreversible Work Chart

If you look on page 275 of the textbook, there is an example problem that shows that the pressure did drop by cooling. However, this takes place before any of the expansion work is actually done, so it is a vertical line. This line could have just as easily not been there, but it is just trying to show that w=pΔv=0 because Δv=0. Then the external pressure stays constant which is why it remains a horizontal line as the volume increases.

William Xu Dis 1D
Posts: 31
Joined: Fri Sep 29, 2017 7:05 am

### Re: Irreversible Work Chart

The vertical brown line just shows that before the expansion, the external pressure was lowered to a certain amount, then the horizontal line afterward represents that the external pressure stayed constant at that amount.