PhysicsLAB AP Free Response Question
2009 B4

The cylinder represented above contains 2.2 kg of water vapor initially at a volume of 2.0 m3 and an absolute pressure of 3.0 x 105 Pa. This state is represented by point A in the PV diagram below. The molar mass of water is 18 g, and the water vapor can be treated as an ideal gas.
 
 
 (a) Calculate the temperature of the water vapor at point A.

The absolute pressure of the water vapor is increased at constant volume to 4.0 x 105 Pa at point B, and then the volume of the water vapor is increased at constant pressure to 2.5 m3 at point C, as shown in the PV diagram.
 
 (b) Calculate the temperature of the water vapor at point C.

 (c) i. Does the internal energy of the water vapor for the process A → B → C increase, decrease, remain the same?

 (c) ii. Justify your choice.

 (d) Calculate the work done on the water vapor for the process A → B → C.





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