1. A 4 kg mass of gas expands adiabatically and does 20 J of work. What is the change in the gas's internal energy?

 

a. -20 J

b. -5 J

c. zero

d. +20 J

 

Answer: _____

 

 

2. What is the change in entropy when 108 grams of silver melt completely at 961^oC? (The heat of fusion of silver is 8.82 x 10⁴ J/kg.)

 

a. 5.53 J/K

b. 7.72 J/K

c. 9.91 J/K

d. 12.1 J/K

 

Answer: _____

 

 

3. A block of ice of mass 1 kg at 273 K melts, taking in 80,000 cal of heat from the air. Which of the following best describes what happens to the ice-air system?

 

a. Entropy increased

b. Entropy decreased

c. Entropy has not changed

d. Work is converted to energy

 

Answer: _____

 

 

4. A steam turbine operates at a boiler temperature of 450 K and an exhaust temperature of 300 K. What is the maximum theoretical efficiency of this system?

 

a. 24%

b. 50%

c. 33.3%

d. 66.7%

 

Answer: _____

 

 

5. How much work is required, using an ideal Carnot refrigerator, to remove 1 J of heat energy from helium at 4 K and eject this heat to a room temperature (293 K) environment?

 

a. 13.9 J

b. 26.7 J

c. 52.6 J

d. 72.3 J

 

Answer: _____

 

 

6. Suppose that 1 kg of water, initially at 350 K, is turned into steam at 373 K. What is the change in entropy? (L_v = 2.26 x 10⁶ J/kg; c_water = 4186 J/(kg C^o)

 

a. 6060 J/K

b. 6070 J/K

c. 6320 J/K

d. 6330 J/K

 

Answer: _____

 

 

7. In an adiabatic process, what happens?

 

a. No work is done by, or on, the system.

b. The internal energy of the system does not change.

c. No heat is lost or gained.

d. None of the above.

 

Answer: _____

 

 

8. According to the Second Law of Thermodynamics, which of the following applies to the heat received from a high temperature reservoir by a heat engine operating in a complete cycle?

 

a. The heat must be completely converted to work.

b. It equals the entropy increase.

c. It is converted completely into thermal energy.

d. It cannot be completely converted into work.

 

Answer: _____

 

 

9. A Carnot engine is operated as a refrigerator, taking in 18 J of heat every second and expelling 20 J into a 23^oC room. What is the temperature inside the refrigerator?

 

a. 15.4^oC

b. 3.33^oC

c. -6.62 ^oC

d. -15.4 ^oC

 

Answer: _____

 

 

10. What is the theoretical efficiency of a Carnot engine that operates between 600 K and 300 K?

 

a. 100%

b. 50%

c. 25%

d. None of the above

 

Answer: _____

 

 

11. If the theoretical efficiency of a Carnot engine is to be 100%, the cold reservoir must be what?

 

a. At absolute zero

b. At 0 ^oC

c. At 100 ^oC

d. Infinitely hot

 

Answer: _____

 

 

12. Three moles of an ideal gas expand at a constant pressure of 4 x 10⁵ Pa from 0.020 to 0.050 m³. What is the work done by the gas?

 

a. 1.2 x 10⁴ J

b. 2.1 x 10⁴ J

c. 3.5 x 10⁴ J

d. 4.2 x 10⁴ J

 

Answer: _____