How can we say that a system is reversible or irreversible if not stated?
I encountered a book example wherein a piston cylinder device encounters an isobaric process and experiences a transfer of heat to the system. And the change of entropy is to be determined.
In this problem, I first thought that the the entropy balance would be Q/T +(Sgenerated) = Delta S. In other words, the total change in entropy between the system boundary and the entropy generated by the system is equal to the change in entropy. But I was wrong, in the book it stated that the entropy generated within the system will not be accounted for the equation since no irreversibilities occured in the system boundary during the process.
This is where I am confused, how can we know if irreversibilities occured within the system boundary? Is it because the system underwent an isobaric process or is it a different factor? While it was not stated that no irreversibilities occured making the process reversible.
And how would we know if the system undergoes an irreversible or irreversible process if not stated? Is it by intuition itself?
I know that the entropy generated by the system would be zero if it undergoes a reversible process. I just find it hard to know when it would occur.