Entropy of Surroundings

[Bella Wachter 1A]

When is ∆S surr equal to 0? I know usually, it will be equal to - ∆H / T or -q rev / T, but when will it equal zero?

I think it was for irreversible free expansions, but I'm not 100% sure.

[Benjamin Chen 1H]

∆S surr = 0 when the process is an Isothermal and Irreversible Free Expansion. No work is being done on or by the surroundings and no net heat is transferred.

[Jarrett Sung 3B]

You're right! Irreversible free expansions, when isothermal as well, have no change in enthalpy.

[Kyle Walsh 2J]

Hi! I'm pretty sure that you're correct, delta S of the surroundings only equals zero for isothermal, irreversible free expansions. Since the enthalpy change is zero, so is the change in entropy. Hope this helps!