An insulated piston-cylinder device initially contains 300 L of air at 120 kPa and 17C. Air is

Question:

An insulated piston-cylinder device initially contains 300 L of air at 120 kPa and 17°C. Air is now heated for 15 min by a 200-W resistance heater placed inside the cylinder. The pressure of air is maintained constant during this process. Determine the entropy change of air, assuming
(a) Constant specific heats and
(b) Variable specific heats.