Calculate Work (w) for Isothermal Gas Expansion/Compression

[IoFawkes]

Homework Statement

Calculate Work(w) when 6.5L of an ideal gas at an initial pressure of 34.3atm is expanded or compressed isothermally to a final volume of 34.3L reversibly. Answer in J

Homework Equations

PV=nRT
P1V1=P2V2
w=-nRT In(V2/V1)

The Attempt at a Solution

Using w=-nRT In(V2/V1)
I'm not given mols or T, I know T=constant, since it's isothermal
Can I use PV=nRT and substitute (PV) in for (nRT) in the equation: w=-nRT In(V2/V1) ?
If so, what should I use for values of P and V? Final/Initial/delta?

Io

PS: This may be in the wrong place, the boundary seems unclear in Chem/Phys or Phys/Chem studies.

 

[TSny]

Welcome to PF!

Can I use PV=nRT and substitute (PV) in for (nRT) in the equation: w=-nRT In(V2/V1) ?

Yes

If so, what should I use for values of P and V? Final/Initial/delta?

How does PV in the initial state compare to PV in the final state?

 

[IoFawkes]

How does PV in the initial state compare to PV in the final state?

P1V1=P2V2 so it doesn't matter which I use as long as P and V are both initial values, or final values. Correct?
EDIT: Except it's asking for work done, so would it be the Change in Pressure and Volume?
Io

 

[TSny]

P1V1=P2V2 so it doesn't matter which I use as long as P and V are both initial values, or final values. Correct?

Yes

EDIT: Except it's asking for work done, so would it be the Change in Pressure and Volume?

nRT is a constant for an isothermal process. At any point along the process, nRT has the same value. The ideal gas law tells us that for any state, nRT = PV. So, nRT for the isothermal process equals PV evaluated for any state along the isothermal process.

nRT would not correspond to a change in PV.

 

[IoFawkes]

nRT is a constant for an isothermal process. At any point along the process, nRT has the same value. The ideal gas law tells us that for any state, nRT = PV. So, nRT for the isothermal process equals PV evaluated for any state along the isothermal process.

nRT would not correspond to a change in PV.

Ah, that makes sense, thanks! How wonderful a change in perspective.

Io