Exam 15: Thermodynamics

A fixed amount of ideal gas is compressed isothermally.Which entry in the table below correctly depicts the sign of the work done, the change in the internal energy, and the heat exchanged with the environment? work done change in internal energy heat exchanged

Two moles of a confined ideal monatomic gas begin at state A on the pressure-volume graph and follow the path shown to state D.If the temperature of the gas at A is 54 K, what is the temperature of the gas at D?

15-3 An ideal monatomic gas expands isobarically from state A to state B.It is then compressed isothermally from state B to state C and finally cooled at constant volume until it returns to its initial state A. -How much work is done on the gas in going from B to C?

Two engines are identical except that engine A is two years old and engine B is new.If engine A does 15% less work than engine B under identical operating conditions, what is the ratio of the efficiencies of the two engines, e_A/e_B?

Which one of the following situations is a direct application of the Zeroth Law of Thermodynamics?

15-5 A heat engine operates between a hot reservoir at 1500 K and a cold reservoir at 500 K.During each cycle, 1.0 × 10⁵ J of heat is removed from the hot reservoir and 5.0 × 10⁴ J of work is performed. -Determine the change in entropy of the cold reservoir.

15-2 An ideal monatomic gas originally in state A is taken reversibly to state B along the straight-line path shown in the pressure-volume graph. -Suppose that the same gas is originally in state A as described above, but its volume is increased isothermally until a new volume of 3.0 liters is reached.Which one of the following statements for this isothermal process is false?

15-4 Two moles of an ideal gas have an initial Kelvin temperature T_i and absolute pressure P_i.The gas undergoes a reversible isothermal compression from an initial volume V_i to a final volume 0.5V_i. -How much heat is exchanged with the environment? If heat is exchanged, is it absorbed or released?

Which one of the following statements best describes the operation of a heat engine?

A heat engine operates in a Carnot cycle between reservoirs of temperatures 1000 K and 400 K.It is found to discharge 20 J of heat per cycle to the cold reservoir.What is the work output per cycle?

What is the ratio of the internal energy of the gas in state C to that in state A?

In an isothermal and reversible process, 945 J of heat is removed from a system and transferred to the surroundings.The temperature is 314 K.What is the change in entropy of the system?

15-3 An ideal monatomic gas expands isobarically from state A to state B.It is then compressed isothermally from state B to state C and finally cooled at constant volume until it returns to its initial state A. -What is the temperature of the gas when it is in state B?

A 1.00-kg sample of steam at 100.0 °C condenses to water at 100.0 °C.What is the entropy change of the sample if the heat of vaporization of water is 2.26 × 10⁶ J/kg?

15-7 An ideal monatomic gas expands isothermally from state A to state B.The gas then cools at constant volume to state C.The gas is then compressed isobarically to D before it is heated until it returns to state A. -What is the internal energy of the gas at point B?

What are the SI units of the product of pressure and volume, PV?

15-6 A container holding 1.2 kg of water at 20.0 °C is placed in a freezer that is kept at -20.0 °C.The water freezes and comes into thermal equilibrium with the interior of the freezer. -Which of the following samples exhibits the highest degree of entropy?

Enclosed beneath the moveable piston in the drawing is 4.8 moles of a monatomic ideal gas.The gas performs work on the piston as 2300 J of heat are added from the surroundings.During the process, the temperature of the gas decreases by 45 K.How much work does the gas perform?

Complete the following statement: The first law of thermodynamics states that

15-5 A heat engine operates between a hot reservoir at 1500 K and a cold reservoir at 500 K.During each cycle, 1.0 × 10⁵ J of heat is removed from the hot reservoir and 5.0 × 10⁴ J of work is performed. -If the coefficient of performance for a refrigerator is 5.0 and 72 J of work are done on the system, how much heat is rejected to the room?