An insulated 5-m3 rigid tank contains air at 500 kPa and 57C. A valve connected to the

Question:

An insulated 5-m3 rigid tank contains air at 500 kPa and 57°C. A valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 200 kPa. The air temperature during this process is maintained constant by an electric resistance heater placed in the tank.
Determine
(a) The electrical energy supplied during this process and
(b) The total entropy change.