When to use "W = -nrt" and "W = -pdV"

[AndresElizarraras 2A]

Can anyone help me identify when we use the equations W = - nrt and when we use W = -pdv

W, of course, means work in this context.

Thank you!

[Ankit Budhiraja 3D]

Considering that there are these two equations for work, I think their usage is dependent on which variable you are given in the context of a problem. Specifically, if you have the variables pertaining to one of the equations rather than the other, you would be able to use them to solve for work. Basically, based on this, I understand that the usage of each of these work equations is based upon the context of the question and what is already being given.

[Eleanor_C_1I]

Like the previous reply notes, I think this depends on the information given in the problem. n refers to moles whereas p represents pressure so your usage of these 2 equations would depend on which you were given. Additionally, we know we can convert between moles and pressure using PV=nRT, depending on what other info we have as well.

[AliciaRoice_1K]

I agree with Eleanor. Both equations use distinctly different variables, so the -nrt equation would be more useful when you are given an amount in moles, and -pdV would be more appropriate when you are given a pressure and change in volume, such as with a cylindrical piston problem.

[Cylin Wang 2H]

As a follow-up question. Will this course involve calculating work for liquids and solids? I've been wondering that because both these formulas do not work for liquids and solids (W=-nrt relies on ideal gas law; dV=0.)