Irreversible problem

[morgantolbert]

So when we consider something as irreversible and has free expansion, we say that w = 0 and q = 0, or that our delta S for surroundings is equal to 0. But how do we still have a value for delta S of the system?

[Sei Lam 3F]

Hi! ΔS (with no subscript) typically refers to ΔSsys, the ΔS of the system. which is different from ΔSsurr. ΔStot = ΔSsys + ΔSsurr. Thus, even if there is no change in entropy of the surroundings, the entropy of the system can have a value.