### w=-PdeltaW

Posted:

**Sat Mar 16, 2019 10:34 pm**Can someone explain when we use the equation w=-PdeltaW? I saw this equation but I do not know how to apply it.

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=130&t=45123

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Posted: **Sat Mar 16, 2019 10:34 pm**

Can someone explain when we use the equation w=-PdeltaW? I saw this equation but I do not know how to apply it.

Posted: **Sat Mar 16, 2019 10:35 pm**

The equation is w=-PdeltaV and you can use this equation when the pressure is constant and you need to find how much work is being done on the system by expansion

Posted: **Sat Mar 16, 2019 10:44 pm**

This equation is w==P deltaV, this is used when you have a constant pressure and are asked to find the work that the system performed and will be given the two values for the different volumes.

Posted: **Sat Mar 16, 2019 11:25 pm**

It can also be used in the equation of delta U=q+w. You can substitute w with -PdeltaV if w is not given to you in the problem.

Posted: **Sun Mar 17, 2019 5:30 pm**

When the system is under constant pressure, this equation gives you the work done by the expansion or compression of the gases. Think of a piston changing the volume of enclosed gases, as it can be derived using PV=nRT so change in moles of gas*n*R*T can also be used accordingly.

Posted: **Sun Mar 17, 2019 5:32 pm**

you use it for irreverible reactions. usually youre given the external pressure pushing onto the system and you need to find the work of the systemm pushing out against the external pressure. and its w = -pdeltav