# Homework Help: Calculating Reversible Work

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1. Jan 10, 2016

### albertov123

1. The problem statement, all variables and given/known data
A rigid and evacuated container of volume V that is surrounded by atmosphere (P0, T0). At some point neck valve opens and atmospheric air gradually fills the container. The wall of container is thin enough so that eventually the trapped air and atm reach thermal equilibrium. The neck valve remains open, therefore at the end the trapped air and atmosphere are also in mechanical equilibrium. Calculate the reversible work and irreversibility.

2. Relevant equations

3. The attempt at a solution

From the first law Q + minhin = m2u2

Qout = P0.V

Sgen=Q/T=P0.V/T0

I = T0S = P0.V = I

I = Wrev - Wirrev

How can I find reversible work? I assumed work is zero in first law. But which work was that irreversible or reversible I don't know.

Last edited: Jan 10, 2016
2. Jan 11, 2016

### Staff: Mentor

The irreversible work is the shaft work, which you correctly determined to be zero. The reversible work is a theoretical quantity, representing the work that could have been done. The irreversibility is the lost work.