Why is work zero when an insulated box reaches equilibrium?

[princejan7]

Homework Statement

"An insulated box is initially divided by a frictionless, thermally conducting piston. One side of the piston is 1.5(m^3) of air at 400k, 4bar. The other side is 1.5(m^3) of air at 400K,2 bar
The piston is released and equilibrium is attained, with the piston experiencing no change of state"


the solution assumes W=0. why is this?

Homework Equations

The Attempt at a Solution

 

[dauto]

What solution? You didn't post any solution.

 

[princejan7]

What solution? You didn't post any solution.

here

 

[dauto]

That's the work for the entire system, not the work between the two chambers. Since the entire system is in a isolated box, there is no external work or heat.