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Reversible and Irreversible

Posted: Wed Feb 05, 2020 12:32 pm
by Karina Kong 2H
I get that reversible reactions change infinitesimally, but why does it have greater changes in internal energy than irreversible reactions?

Re: Reversible and Irreversible

Posted: Wed Feb 05, 2020 7:29 pm
by AArmellini_1I
Because for infinitesimally small expansion, work must be done and equilibrium must be regained. This repeats over and over and this creates a decreasing curve where as irreversible expansion occurs immediately so work occurs instantly only once and equilibrium is only regained once (this creates a vertical drop then flattening out of the graph). Another way to see that reversible does more work than irreversible is the area under the curve for reversible is much greater than the area under the curve of the irreversible (or square-like shape).

Re: Reversible and Irreversible

Posted: Sat Feb 08, 2020 10:56 pm
by Shail Avasthi 2C
AArmellini_1I wrote:Because for infinitesimally small expansion, work must be done and equilibrium must be regained. This repeats over and over and this creates a decreasing curve where as irreversible expansion occurs immediately so work occurs instantly only once and equilibrium is only regained once (this creates a vertical drop then flattening out of the graph). Another way to see that reversible does more work than irreversible is the area under the curve for reversible is much greater than the area under the curve of the irreversible (or square-like shape).


Here's an image that demonstrates this visually:

Image

Re: Reversible and Irreversible

Posted: Sat Feb 08, 2020 11:03 pm
by BritneyP- 2c
For a given initial and final volume,more expansion work is done when the temperature is high than low. For a given volume and amount of gas- phase molecules, a higher temperature corresponds to a higher gas pressure, and so the expansion takes place against a stronger force and therefore has to do more work. More expansion work is also done if the V2 is much greater than V1