Deck 16: Thermodynamics

Question 1

Which of the processes on a monatomic ideal gas given below will result in the temperature of the gas increasing? W is the work done by the gas.

A) a process where Q = W
B) a process where
C) a process where Q = 2W
D) None of the above will increase the temperature of the gas.

Answer 1

a process where Q = 2W

Question 2

In an isobaric process 3.6 * 10⁴ J of work is done on a quantity of gas while its volume changes from 2.3 m³ to 1.1 m³. What is the pressure during this process?

A) 1.2 * 10⁴ Pa
B) 2.4 * 10⁴ Pa
C) 3.0 *10⁴ Pa
D) 8.3 *10⁴ Pa

Answer 2

3.0 *10⁴ Pa

Question 3

A 4-mol ideal gas system undergoes an adiabatic process where it expands and does 28 J of work on its environment. What is its change in internal energy?

A) "28 J"
B) "-28 J"
C) "zero"
D) "-7 J"

Answer 3

"-28 J"

Question 4

Area on a P-V diagram has units associated with:

A) energy.
B) momentum.
C) temperature.
D) change in temperature.

Question 5

If an ideal gas does positive work on its surroundings, we may assume, with regard to the gas, that its:

A) temperature increases.
B) volume increases.
C) pressure increases.
D) internal energy decreases.

Question 6

According to the first law of thermodynamics, the sum of the heat gained by a system and the work done on that same system is equivalent to which of the following?

A) entropy change
B) internal energy change
C) temperature change
D) specific heat

Question 7

A 4-mol ideal gas system undergoes an adiabatic process where it expands and does 28 J of work on its environment. How much heat is received by the system?

A) "-20 J"
B) "zero"
C) "+28 J"
D) "+7 J"

Question 8

The adiabatic index, , of a gas is given by which of the following?

A) C_P /C_V
B) C_V /C_P
C) C_P - C_V
D) C_P + C_V

Question 9

A system has an increase in internal energy of 60 J while 90 J was removed from the system by heat. How much work was involved during this process and was it done on the system or done on its environment?

A) 30 J on the system
B) 30 J on the environment
C) 150 J on the system
D) 150 J on the environment

Question 10

A closed 2.0-L container holds 3.0 mol of an ideal gas. If 150 J of heat is added, what is the change in internal energy of the system?

A) zero
B) 100 J
C) 150 J
D) 200 J

Question 11

A 2.0-mol ideal gas system is maintained at a constant volume of 4.0 L. If 200 J of heat is added, what is the work done on the system?

A) zero
B) 5.0 J
C) -6.7 J
D) 20 J

Question 12

In an isovolumetric process where the pressure increases, are the heat absorbed, work done by the system, and the change in internal energy of the system positive, negative, or zero?

A) Q is +, W is +, and $\Delta$ U is +.
B) Q is +, W is -, and $\Delta$ U is 0.
C) Q is +, W is 0, and $\Delta$ U is +.
D) Q is -, W is 0, and $\Delta$ U is -.

Question 13

On a P-V diagram, an _____ process is represented by a horizontal line.

A) isobaric
B) isothermal
C) isovolumetric
D) adiabatic

Question 14

In an isovolumetric process by an ideal gas, the system's heat gain is equivalent to its change in:

A) temperature.
B) volume.
C) pressure.
D) internal energy.

Question 15

An adiabatic expansion refers to the fact that:

A) no heat is transferred between a system and its surroundings.
B) the pressure remains constant.
C) the temperature remains constant.
D) the volume remains constant.

Question 16

In an isothermal process for an ideal gas system (where the internal energy doesn't change), which of the following choices best corresponds to the value of the work done by the system?

A) its heat intake
B) twice its heat intake
C) the negative of its heat intake
D) twice the negative of its heat intake

Question 17

A system is acted on by its surroundings in such a way that it receives 50 J of heat while simultaneously doing 70 J of work. What is its net change in internal energy?

A) "70 J"
B) "-20 J"
C) "zero"
D) "20 J"

Question 18

During an isobaric process which one of the following does not change?

A) volume
B) temperature
C) internal energy
D) pressure

Question 19

On a PV diagram, 2 curves are plotted, both starting at the same point (P₁, V₁) and both ending at the same increased volume (V₂). One curve is for an isothermal process; the other is for an adiabatic process. Except for the common starting point, which curve is the upper one?

A) The isothermal process curve will always be the upper one.
B) The adiabatic process curve will always be the upper one.
C) Since they start at the same point and end at the same volume, they will coincide.
D) The isothermal one will start out higher, but the adiabatic one will eventually cross it.

Question 20

The volume of an ideal gas changes from 0.40 to 0.55 m³ although its pressure remains constant at 50,000 Pa. What work is done by the system ON its environment?

A) "-7500 J"
B) "-200,000 J"
C) "7500 J"
D) "200,000 J"

Question 21

Three Carnot engines operate between temperature reservoirs as follows: Engine A: T_h = 1300 K, T_c = 1000 K; Engine B: T_h = 1000 K, T_c = 700 K; Engine C: T_h = 500 K, T_c = 350 K. Which two engines have the same thermal efficiency?

A) A and B
B) B and C
C) A and C
D) No two have the same thermal efficiency.

Question 22

An electrical generating plant operates at a boiler temperature of 200 $\degree$ C and exhausts the unused heat into a nearby river at 20 $\degree$ C. What is the maximum theoretical efficiency of the plant? (0 $\degree$ C = 273 K)

A) 61%
B) 38%
C) 21%
D) 41%

Question 23

Consider a Carnot cycle starting at the state of highest pressure and smallest volume. Call the isothermal expansion from this state step 1, the adiabatic expansion which follows step 2, the isothermal compression that then follows step 3, and the adiabatic compression which returns the system to the initial state step 4. In which steps does the internal energy of the system increase?

A) 1 and 2
B) 3 and 4
C) 1 and 3
D) 2 and 4

Question 24

The maximum theoretical thermodynamic efficiency of a heat engine operating between hot and cold reservoirs is a function of which of the following?

A) hot reservoir temperature only
B) cold reservoir temperature only
C) both hot and cold reservoir temperatures
D) None of the above choices are valid.

Question 25

An electrical generating plant operates at a boiler temperature of 220 $\degree$ C and exhausts the unused heat into a nearby river at 19 $\degree$ C. If the generating plant has a power output of 800 megawatts (MW) and if the actual efficiency is 3/5 the theoretical efficiency, how much heat per second must be delivered to the boiler? (0 $\degree$ C = 273 K)

A) 5200 MW
B) 1810 MW
C) 3270 MW
D) 2620 MW

Question 26

A heat engine operating between a pair of hot and cold reservoirs with respective temperatures of 500 K and 300 K will have what maximum efficiency?

A) 60%
B) 50%
C) 40%
D) 30%

Question 27

A heat engine receives 6000 J of heat from its combustion process and loses 3600 J through the exhaust and friction. What is its efficiency?

A) 33%
B) 40%
C) 67%
D) 73%

Question 28

A turbine takes in 1000 K steam and exhausts the steam at a temperature of 400 K. What is the maximum theoretical efficiency of this system?

A) 24%
B) 40%
C) 50%
D) 60%

Question 29

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) must be completely converted to work
B) equals the entropy increase
C) converted completely into internal energy
D) cannot be completely converted to work

Question 30

A thermodynamic process that happens very quickly tends to be:

A) isobaric.
B) isothermal.
C) isovolumetric.
D) adiabatic.

Question 31

An electrical power plant manages to send 88% of the heat produced in the burning of fossil fuel into the water-to-steam conversion. Of the heat carried by the steam, 30% is converted to the mechanical energy of the spinning turbine. Which of the following choices best describes the overall efficiency of the heat-to-work conversion in the plant (as a percentage)?

A) greater than 88%
B) 64%
C) 30%
D) less than 30%

Question 32

In an isochoric process where the pressure increases from to , does the internal energy of the system increase or decrease and does the temperature increase or decrease?

A) The internal energy increases and the temperature decreases.
B) The internal energy increases and the temperature increases.
C) The internal energy decreases and the temperature decreases.
D) The internal energy decreases and the temperature increases.

Question 33

A heat engine exhausts 4000 J of heat while performing 2000 J of useful work. What is the efficiency of the engine?

A) 15%
B) 33%
C) 40%
D) 60%

Question 34

A cylinder containing an ideal gas has a volume of 3.0 m³ and a pressure of 1.0 *10⁵ Pa at a temperature of 300 K. The cylinder is placed against a metal block that is maintained at 900 K, and the gas expands as the pressure remains constant until the temperature of the gas reaches 900 K. The change in internal energy of the gas is +6.0 *10⁵ J. How much heat did the gas absorb?

A) 0
B) 6.0 * 10⁵ J
C) 12 * 10⁵ J
D) 9.0 * 10⁵ J

Question 35

A 5-mol ideal gas system undergoes an adiabatic free expansion (a rapid expansion into a vacuum), going from an initial volume of 10 L to a final volume of 20 L. How much work is done on the system during this adiabatic free expansion?

A) "-50 J"
B) "-10 J"
C) "zero"
D) "+50 J"

Question 36

During each cycle of operation a refrigerator absorbs 45 cal from the freezer compartment and expels 85 cal to the room. If one cycle occurs every 8.0 s, how many minutes will it take to freeze 500 g of water, initially at 0 $\degree$ C? (L_v = 80 cal/g)

A) 800 min
B) 4400 min
C) 120 min
D) 150 min

Question 37

Which of the following increases the internal energy of a solid metal rod?

A) raising it to a greater height
B) throwing it through the air
C) having the rod conduct heat
D) having the rod absorb heat

Question 38

If a heat engine has an efficiency of 30% and its power output is 600 W, what is the rate of heat input from the combustion phase?

A) 1800 W
B) 2400 W
C) 2000 W
D) 3000 W

Question 39

A quantity of monatomic ideal gas expands adiabatically from a volume of 2.0 liters to 4.0 liters. If the initial pressure is P₀, what is the final pressure?

A) 9.0P₀
B) 6.2P₀
C) 0.31P₀
D) 0.16P₀

Question 40

Heat is applied to an ice-water mixture to melt some of the ice. In this process:

A) work is done by the ice-water mixture.
B) the temperature increases.
C) the internal energy increases.
D) all of the above are correct.

Question 41

On a P-V diagram, if a process involves a closed curve, the area inside the curve represents:

A) internal energy.
B) heat.
C) work.
D) zero.

Question 42

A 2.00-kg block of ice is at STP (0 $\degree$ C, 1 atm) while it melts completely to water. What is its change in entropy? (For ice, L_f = 3.34 *10⁵ J/kg)

A) zero
B) 584 J/K
C) 1220 J/K
D) 2450 J/K

Question 43

Of the following heat engines, which has the highest efficiency?

A) Hero's engine
B) a Carnot engine
C) a car's gasoline engine
D) a truck's diesel engine

Question 44

A 1.0-kg chunk of ice at 0 $\degree$ C melts, absorbing 80,000 cal of heat in the process. Which of the following best describes what happens to this system?

A) increased entropy
B) lost entropy
C) entropy maintained constant
D) work converted to energy

Question 45

The efficiency of a Carnot engine operating between 100 $\degree$ C and 0 $\degree$ C is most nearly:

A) 7%.
B) 15%.
C) 27%.
D) 51%.

Question 46

Suppose a power plant uses a Carnot engine to generate electricity, using the atmosphere at 300 K as the low-temperature reservoir. Suppose the power plant produces an amount of electricity with the hot reservoir at 500 K during Day One and then produces the same amount of electricity with the hot reservoir at 600 K during Day Two. The thermal pollution was:

A) greatest on Day One.
B) greatest on Day Two.
C) the same on both days.
D) zero on both days.

Question 47

An avalanche of ice and snow of mass 2500 kg slides a vertical distance of 160 m down a mountainside. If the temperature of the ice, snow, mountain, and surrounding air are all at 0 $\degree$ C, what is the change in entropy of the universe?

A) 14,000 J/K
B) 10,000 J/K
C) 1400 J/K
D) 1100 J/K

Question 48

When gasoline is burned, it gives off 46,000 J/g of heat energy. If an automobile uses 13.0 kg of gasoline per hour with an efficiency of 18%, what is the average horsepower output of the engine? (1 hp = 746 W)

A) 47 hp
B) 110 hp
C) 67 hp
D) 40 hp

Question 49

According to the first law of thermodynamics, for any process that may occur within an isolated system, which of the following choices applies?

A) entropy remains constant
B) entropy increases
C) entropy decreases
D) None of the above choices apply.

Question 50

The P-V diagram of a cyclic process shows a curve that encloses an area. The work done by the heat engine, represented by the enclosed area, is positive when the path around the area proceeds in which of the following fashions?

A) clockwise
B) counterclockwise
C) It is always positive.
D) It is always negative.

Question 51

A gasoline engine with an efficiency of 40.0% operates between a high temperature T₁ and a low temperature T₂ = 320 K. If this engine operates with Carnot efficiency, what is the high-side temperature T₁?

A) 1070 K
B) 868 K
C) 533 K
D) 457 K

Question 52

Two kilograms of water at 1.00 atm at the boiling point of 100 $\degree$ C is heated until all the water vaporizes. What is its change in entropy? (For water, L_v = 2.26 * 10⁶ J/kg)

A) 12,100 J/K
B) 6060 J/K
C) 3030 J/K
D) 1220 J/K

Question 53

The Carnot cycle consists of a combination of _____ and _____ processes.

A) isobaric, isovolumetric
B) isovolumetric, adiabatic
C) isobaric, isothermal
D) adiabatic, isothermal

Question 54

Which of the following choices best corresponds to what is required by the second law of thermodynamics for any process taking place in an isolated system?

A) entropy decreases
B) entropy remains constant
C) entropy increases
D) entropy equals work done on the system

Question 55

What is the change in entropy ( $\Delta$ S) when two moles of silver (108 g/mole) is completely melted at 961 $\degree$ C? (The heat of fusion of silver is 8.82 *10⁴ J/kg.)

A) 5.53 J/K
B) 7.72 J/K
C) 15.4 J/K
D) 12.1 J/K

Question 56

If one could observe the individual atoms making up a piece of matter and note that during a process of change their motion somehow became more orderly, then one may assume which of the following in regard to the system?

A) increases in entropy
B) decreases in entropy
C) gains in thermal energy
D) positive work done on

Question 57

A Carnot engine runs between a hot reservoir at T_h and a cold reservoir at T_c. If one of the temperatures is either increased or decreased by 3.5 K, which of the following changes would increase the efficiency by the greatest amount?

A) increasing T_h
B) increasing T_c
C) decreasing T_c
D) cannot be determined from information given

Question 58

Which of the following choices is an appropriate unit for measuring entropy changes?

A) J · K
B) N · K
C) J/s
D) J/K

Question 59

In which system is heat usually transferred from the cooler part to the warmer part?

A) a stove as it heats up water
B) a refrigerator that is running
C) an electric fan that is running
D) none of the above, because it is impossible to transfer heat in this manner

Question 60

A 600-MW electric power plant has an efficiency of 30%. It loses its waste heat in large cooling towers. Approximately how much waste heat (in MJ) is discharged to the atmosphere per second?

A) 1400 MJ
B) 1900 MJ
C) 800 MJ
D) 560 MJ

Question 61

You have a P-V diagram for a device going through a cyclic process forming a closed loop on the diagram. How can you tell from the diagram whether the device is acting as a heat engine and not as a refrigerator?

A) The loop is longer than it is high which means it is acting as a refrigerator.
B) The loop is higher than it is long which means it is acting as a refrigerator.
C) The loop proceeds clockwise which means it is acting as a heat engine.
D) The loop proceeds counterclockwise which means it is acting as a heat engine.

Question 62

In an isothermal process where the pressure decreases from to , does the internal energy of the system increase, decrease, or stay the same; and does the entropy of the system increase or decrease?

A) The internal energy decreases and the entropy increases.
B) The internal energy stays the same and the entropy increases.
C) The internal energy decreases and the entropy decreases.
D) The internal energy stays the same and the entropy decreases.

Question 63

The laws of thermodynamics can be related to the following: (i) the measurement of temperature, (ii) the lowest temperature possible, (iii) conservation of energy, and (iv) only part of heat energy available may be turned into work. Which of these involve the first and second law?

A) (i) and (ii)
B) (ii) and (iv)
C) (i) and (iii)
D) (iii) and (iv)

Question 64

The surface of the Sun is at approximately 5700 K, and the temperature of the Earth's surface is about 290 K. What total entropy change occurs when 2000 J of heat energy is transferred from the Sun to the Earth?

A) 5.78 J/K
B) 5.97 J/K
C) 7.24 J/K
D) 6.55 J/K

Question 65

The laws of thermodynamics can be related to the following: (i) the measurement of temperature, (ii) the lowest temperature possible, (iii) conservation of energy, and (iv) only part of heat energy available may be turned into work. Which of these involve the zeroth and third law?

A) (i) and (ii)
B) (ii) and (iv)
C) (i) and (iii)
D) (iii) and (iv)

Question 66

A cylinder containing an ideal gas has a volume of 3.0 m³ and a pressure of 1.0 *10⁵ Pa at a temperature of 300 K. The cylinder is placed against a metal block that is maintained at 900 K and the gas expands as the pressure remains constant until the temperature of the gas reaches 900 K. The change in internal energy of the gas is 9.0 * 10⁵ J. Find the change in entropy of the block associated with the heat transfer to the gas.

A) "0"
B) "+670 J/K"
C) "-1700 J/K"
D) "-1100 J/K"

Question 67

Consider a Carnot cycle starting at the state of highest pressure and smallest volume. Call the isothermal expansion that starts at this state step 1, the adiabatic expansion which follows step 2, the isothermal compression that then follows step 3, and the adiabatic compression which returns the system to the initial state step 4. In which step does the entropy of the system increase?

A) 1
B) 2
C) 3
D) 4

Question 68

Entropy is a measure of the _____ of a system.

A) disorder
B) temperature
C) heat
D) internal energy