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### Reversible vs. Irreversible

Posted: Thu Feb 14, 2019 10:38 am
I'm still having trouble understanding what reversible means for a reaction? What are the different equations you use for a reversible or irreversible?

### Re: Reversible vs. Irreversible

Posted: Thu Feb 14, 2019 2:34 pm
For a reversible reaction, the system is at equilibrium and when it is either compressed or expanded, it does so slowly in infinitely small increments, and you use the equation w = -nRTln(V2/V1) for work. For an irreversible reaction, the reaction is happening under a constant external pressure Pext, and the work equation is w = -P(deltaV).

### Re: Reversible vs. Irreversible

Posted: Thu Feb 14, 2019 3:48 pm
For a reversible reaction, delta S of the system is equal to -delta S of the surrounding because delta S universe is equal to zero. For this reaction, you would use w=-nRTln(V2/V1).

For an irreversible reaction, delta S of the universe is equal to delta S of the system because delta S of the surrounding is equal to zero. For this reaction, you would use w=Pexternal*deltaV.

### Re: Reversible vs. Irreversible

Posted: Thu Feb 14, 2019 6:16 pm
A reversible reaction would also have more work done and is isothermal (temperature remains constant.)
An irreversible reaction would have less work done and is isobaric (pressure remains constant).

### Re: Reversible vs. Irreversible

Posted: Mon Feb 18, 2019 2:18 am
For a reversible reaction, you use w=-nRT ln (v2/v1) and for an irreversible reaction, you use w=-Pex times delta V.

### Re: Reversible vs. Irreversible

Posted: Mon Feb 18, 2019 8:42 am
Just remember that more work is done in an isothermal reversible system than an irreversible system. Think of the work as the integral of the graphs we were shown in class when the irreversible system is basically held at constant P.