Chapter 15: 2MCQ (page 412)
Question: Which is possible: converting (i) 100 J of work entirely into 100 J of heat, (ii) 100 J of heat entirely into 100 J of work?
(a) Only (i) is possible.
(b) Only (ii) is possible.
(c) Both (i) and (ii) are possible.
(d) Neither (i) nor (ii) is possible.
Both (i) and (ii) are possible.
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A 110 g insulated aluminum cup at 35°C is filled with 150 g of water at 45°C. After a few minutes, equilibrium is reached.
(a) Determine the final temperature and
(b) the total change in the entropy.
Question: (I) The low temperature of a freezer cooling coil is\({\bf{ - 8^\circ C}}\)and the discharge temperature is\({\bf{33^\circ C}}\). What is the maximum theoretical coefficient of performance?
Refrigeration units can be rated in “tons.” A 1-ton air conditioning system can remove sufficient energy to freeze 1 ton (2000 pounds = 909 kg) of 0°C water into 0°C ice in one 24-h day. If, on a 35°C day, the interior of a house is maintained at 22°C by the continuous operation of a 5-ton air conditioning system, how much does this cooling cost the homeowner per hour? Assume the work done by the refrigeration unit is powered by electricity that costs $0.10 per kWh and that the unit’s coefficient of performance is 18% that of an ideal refrigerator.\({\bf{1}}\;{\bf{kWh = 3}}{\bf{.60 \times 1}}{{\bf{0}}{\bf{6}}}\;{\bf{J}}\).
1.0 kg of water at 35°C is mixed with 1.0 kg of water at 45°C in a well-insulated container. Estimate the net change in entropy of the system.
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