### w=-PdeltaV

Posted:

**Wed Feb 06, 2019 10:56 pm**For both work equations of w=-nRTln(V2/V1) and w=-PdeltaV, what are all the conditions in which we would use one over the other?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=127&t=41529

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Posted: **Wed Feb 06, 2019 10:56 pm**

For both work equations of w=-nRTln(V2/V1) and w=-PdeltaV, what are all the conditions in which we would use one over the other?

Posted: **Wed Feb 06, 2019 11:01 pm**

Use the equation W=-PdeltaV for a sudden irreversible expansion when work is done against a constant external pressure and temperature changes - less work is done for this pathway.

Ue the other work equation for a reversible expansion, when temperature is constant, external pressure is not constant, and more work is done.

Ue the other work equation for a reversible expansion, when temperature is constant, external pressure is not constant, and more work is done.

Posted: **Fri Feb 08, 2019 9:06 am**

The first equation would only be used for questions that deal with reversible expansion, while the second equation of w=-PdeltaV would only be used for irreversible expansion.

Posted: **Fri Feb 08, 2019 8:59 pm**

The first equation is used in the case of a reversible expansion, meanwhile the second equation is used in the case of an irreversible expansion.

Posted: **Fri Feb 08, 2019 11:49 pm**

The first one is for reversible expansion, and the second one is for irreversible expansion.

Posted: **Sat Feb 09, 2019 12:57 am**

The first one is used when the external pressure is not constant, which is reversible expansion, and the other equation is used when the external pressure is constant, which is irreversible expansion.

Posted: **Sun Feb 10, 2019 4:46 pm**

-PdeltaV would be used if your external pressure is constant, and with irreversible reactions.