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Unformatted text preview: ompressible Substances R134a
0.05 m3
0.8 MPa FIGURE P7–39 7–48C Consider two solid blocks, one hot and the other cold,
brought into contact in an adiabatic container. After a while,
thermal equilibrium is established in the container as a result of
heat transfer. The first law requires that the amount of energy
lost by the hot solid be equal to the amount of energy gained by
the cold one. Does the second law require that the decrease in
entropy of the hot solid be equal to the increase in entropy of
the cold one?
7–49 A 50kg copper block initially at 80°C is dropped
into an insulated tank that contains 120 L of water at 25°C. cen54261_ch07.qxd 11/18/03 9:58 AM Page 337 337
CHAPTER 7
Water 7–55C Starting with the second T ds relation (Eq. 7–26), obtain Eq. 7–34 for the entropy change of ideal gases under the
constantspecificheat assumption.
7–56C Some properties of ideal gases such as internal energy
and enthalpy vary with temperature only [that is, u u(T ) and
h h(T )]. Is this also the case for entropy? Copper
50 kg 7–57C Starting with Eq. 7–34...
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 Spring '09

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