Question

1.As a result of any natural process, the total entropy of any system plus that of its environment As a result of any natural process, the total entropy of any system plus that of its environment?

A) always stays the same. B) sometimes decreases. C) never decreases. D) never increases.

2.According to the second law of thermodynamics, the entropy of any system always increases. According to the second law of thermodynamics, the entropy of any system always increases.

A)True B)False

3. An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt, causing no appreciable change in the temperature of the bath water. Which one of the following statements is true?

A)The entropy of the system (ice plus water) increases because the process is irreversible.

B)The entropy lost by the ice cube is equal to the entropy gained by the water.

C)The net entropy change of the system (ice plus water) is zero because no heat was added to the system. D)The entropy gained by the ice cube is equal to the entropy lost by the water.

E)The entropy of the water does not change because its temperature did not change.

4.An engine manufacturer makes the claim that the engine they have developed will, on each cycle, take 100J of heat out of boiling water at 100∘C, do mechanical work of 80J, and exhaust 20J of heat at 10∘C. What, if anything, is wrong with this claim?

A)There is nothing wrong with this claim because 100J=20J +80 J.

B)An engine would operate by taking in heat at the lower temperature and exhausting heat at the higher temperature.

C)The efficiency of this engine is greater than the ideal Carnot cycle efficiency.

D)This engine violates the first law of thermodynamics because 100 J +20J ≠ 80 J.

E)The heat exhausted must always be greater than the work done according to the second law of thermodynamics.

Answer 1

2.true

=>Second Law of Thermodynamics: In any cyclic process the entropy will either increase or remain the same

=>The second law of thermodynamics states that in every real process the sum of the entropies of all participating bodies is increased. In the idealized limiting case of a reversible process, this sum remains unchanged. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past

3. A. the entropy of system (Ice plus water) increases because the process is irreversible.
Q = Q
?Si = Q/Ti = Q/273

?Sw = Q/Tw = -Q/303

?St = ?Si + ?Sw
?St = Q ( 1/273 - 1/303)
?St = Q ([303- 273] / 303*273)
?St > 0 (entropy of system increase)

4.C)The efficiency of this engine is greater than the ideal Carnot cycle efficiency

1st law of thermpdynamics: Q_H = Wout + Q_c = 80 + 20 = 100J

second law : efficeincy of Carnot cycle E_c = 1 - (T_c / T_H) = 1 - (283k / 373k) = 0.24

efficiency of engine E = Wout / Q_H = 80 / 100 = 0.8 > E_c