Chapter 15: 11CQ. (page 548)
We ordinarily say that ΔU = 0 for an isothermal process. Does this assume no phase change takes place? Explain your answer.
During the transformation of the phase, the temperature remains the same but the state of the system changes. So, the phase change can take place.
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(a) What is the hot reservoir temperature of a Carnot engine that has an efficiency of \({\bf{42}}{\bf{.0\% }}\)and a cold reservoir temperature of \({\bf{27}}{\bf{.0}}\;{\bf{^\circ C}}\)? (b) What must the hot reservoir temperature be for a real heat engine that achieves \({\bf{0}}{\bf{.700}}\) of the maximum efficiency, but still has an efficiency of \({\bf{42}}{\bf{.0\% }}\) (and a cold reservoir at \({\bf{27}}{\bf{.0}}\;{\bf{^\circ C}}\))? (c) Does your answer imply practical limits to the efficiency of car gasoline engines?
Explain how water’s entropy can decrease when it freezes without violating the second law of thermodynamics. Specifically, explain what happens to the entropy of its surroundings.
Definitions of efficiency vary depending on how energy is being converted. Compare the definitions of efficiency for the human body and heat engines. How does the definition of efficiency in each relate to the type of energy being converted into doing work?
Find the increase in entropy of 1.00 kg of liquid nitrogen that starts at its boiling temperature, boils, and warms to 20.0 º C at constant pressure.
A gas-cooled nuclear reactor operates between hot and cold reservoir temperatures of 700ºC and 27.0ºC . (a) What is the maximum efficiency of a heat engine operating between these temperatures? (b) Find the ratio of this efficiency to the Carnot efficiency of a standard nuclear reactor (found in Example 15.4).
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