1. A well-insulated piston cylinder contains 5kg of saturated mixture water at 150kPa. Initially, three-quarter of the mass is in vapor phase. After a process, the pressure and temperature in the tank change to 200kPa and 400oC. Determine the entropy change of the water.
2. Air in a piston cylinder is expanded from 2 m3 and 25oC to 5m3 and 100oC. Determine the specific entropy change.
3. In a piston cylinder device, 5kg of Air at 200kPa and 227oC is compressed to 500kPa at 100oC. Determine the entropy change of the air. If during this process, there is only 200kJ transferred to the surrounding of 20oC, determine the entropy change of the surrounding. Will this process occur or not according to the second law of thermodynamics?
4. Nitrogen at 900kPa and 300oC is expended adiabatically and reversibly in a closed system to 100kPa. Determine the minimum nitrogen temperature after the expansion.