A piston-cylinder device initially contains 10 kg of saturated steam at P = 2 MPa. Heat is added and the steam expands until its temperature is 673.15 K. The external and internal pressure are both 2 MPa throughout the process. How much heat was added?
A. 3.48 MJ
B. 4.52 MJ
C. 20.4 MJ
D. 2.0 MJ
E. Insufficient information to solve
A. Incorrect. This is the change in internal energy. But expansion work also occurs.
B. Correct.
C. Incorrect. You are misreading the steam tables. The initial state is saturated steam, not liquid water.
D. Incorrect. You are making a calculation or algebra error somewhere.
E. Incorrect. There is sufficient information to solve the problem.
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