Is entropy of surroundings a state function?
In reality, when we talk about the surroundings, what we are referring to isn't really the entire universe, outside what we call &quot;the system.&quot;  What we are really referring to is a subregion of the entire universe, wherein it is possible to carry out changes reversibly without encompassing the whole rest of the universe.  So, when we talk about the entropy change of the surroundings, we are not including spontaneous processes occurring light years away in other galaxies.  And, when we say that the entropy change for system plus the surroundings is zero, we are really only including the selected subregion of surroundings chosen to represent our sub-universe.