question about irreversible systems

[Henry_2A]

Hi!
What did Professor Lavelle mean when he said that in a system that is irreversible, the external pressure will be lower than the internal pressure, meaning less work is done. Why is it less work?

[Grace Chang 1E]

Hello!

If I'm understanding it correctly, less work is done in an irreversible process because the system is pushing on only that significantly-lower external pressure (like 0.5 atm in the example). On the other hand, in a reversible process, your system still does work until the external pressure decreases (from 1 atm --> 0.5 atm) . . . however, because you are decreasing the external pressure by *extremely* small values (and accordingly, increasing the volume by *extremely* small values as well), you will be able to take into account all those steps that the system does work on. For example, you will get all of the times that the system does work on 0.999999 atm, 0.999998 atm, 0.999997 atm, etc.

Please correct me if any of this sounds wrong!