2-kg of saturated water vapor at 600 kPa are contained in a piston-cylinder device. The water expands adiabatically until the pressure is 100 kPa and is said to produce 700 kJ of work output.
(a) Determine the entropy change of the water, in kJ/kg·K.
(b) Is this process realistic? Using the T-s diagram for the process and the concepts of second law, support your answer.