Deck 15: Thermodynamics

Question 1

A system performs 800 J of work while taking in 500 J of heat.What is the change in internal energy of the system?

A) not possible.
B) 300 J
C) -300 J
D) 1300 J
E) -1300 J

Answer 1

-300 J

Question 2

10 joules of heat energy are transferred to a sample of ideal gas at constant pressure.As a result,the internal energy of the gas

A) increases by 10 J
B) increases by less than 10 J
C) increases by more than 10 J
D) remains unchanged.

Answer 2

increases by less than 10 J

Question 3

When an ideal gas adiabatically expands

A) the temperature of the gas changes.
B) the internal energy of the gas does not change.
C) work is not done on or by the gas.
D) no heat is given off or taken in by the gas.

Answer 3

no heat is given off or taken in by the gas.

Question 4

When an ideal gas is compressed isothermally:

A) the internal energy of the gas does not change.
B) the work done on the gas is zero.
C) heat flows into the gas.
D) the temperature of the gas increases.

Question 5

In the first law of thermodynamics ( $\Delta$ U = Q + W),the variables Q and W stand for

A) the heat flow out of the system and the work done on the system.
B) the heat flow out of the system and the work done by the system.
C) the heat flow into the system and the work done by the system.
D) the heat flow into the system and the work done on the system.

Question 6

On a PV diagram where pressure is in atmospheres and V is in liters the area is measured in liter-atmospheres.What is the number of Joules in 1.00 liter-atmosphere?

A) 101.3
B) 83.1
C) 65.2
D) 22.4
E) 15.7

Question 7

The internal energy of a system increases by 500 J while 610 J of work are performed on it.What was the heat flow into or out of the system?

A) -1110 J
B) 1110 J
C) -110 J
D) 110 J

Question 8

If 30 kJ of heat flows out of a system and 15 kJ of work is done by the system,then what is the change in internal energy?

A) 85 kJ
B) 70 kJ
C) 45 kJ
D) 15 kJ
E) 10 kJ

Question 9

A kilogram of water (c = 4.186 kJ/kg $^{\circ}$ C)is stirred using a 400 watt device for 5 minutes.At the end of this time the temperature of the water has increased by 15 $^{\circ}$ C.How much heat was lost to the surroundings?

A) 90.1 kJ
B) 57.3 kJ
C) 82.6 kJ
D) 38.9 kJ

Question 10

Using 0.0200 mol of an ideal monatomic gas,an isochoric process from A (230 kPa,1.00 L)to B (98 kPa,1.00 L)results in what change in internal energy?

A) -200 J
B) +200 J
C) -375 J
D) +375 J

Question 11

If 1.00 mol of oxygen is heated at constant pressure of 1.00 atm from 10.0 $^{\circ}$ C to 25.0 $^{\circ}$ C.From the first law,calculate the change of internal energy of the gas in this process.

A) 312 J
B) 291 J
C) 365 J
D) 155 J

Question 12

A toy steam engine has a mass of 1.00 kg.The toy starts from rest and reaches a velocity of 4.00 m/s in a time of 3.00 seconds while covering a distance of 4.50 meters.During that time the toy takes in 30 J of heat.What is the change in the internal energy of the toy?

A) -52.0 J
B) +52.0 J
C) -22 J
D) +22 J

Question 13

If 30 kJ of heat flows into a system and the internal energy increases by 15 kJ,then what is the work done by or on the system?

A) +85 kJ
B) +65 kJ
C) -65 kJ
D) +15 kJ
E) -15 kJ

Question 14

If 1.00 mol of oxygen is heated at constant pressure of 1.00 atm from 10.0 $^{\circ}$ C to 25.0 $^{\circ}$ C.How much heat is absorbed by the gas?

A) 389 J
B) 544 J
C) 436 J
D) 288 J

Question 15

If 50 kJ of heat flows into a system and 35 kJ of work is done by the system,then what is the change in internal energy?

A) 85 kJ
B) 70 kJ
C) 65 kJ
D) 15 kJ
E) 10 kJ

Question 16

If 1.00 mol of oxygen is heated at constant pressure of 1.00 atm from 10.0 $^{\circ}$ C to 25.0 $^{\circ}$ C.What is the change of volume of the gas in this process?

A) 1.23 L
B) 0.86 L
C) 1.88 L
D) 2.09 L

Question 17

If 1.00 mol of oxygen is heated at constant pressure of 1.00 atm from 10.0 $^{\circ}$ C to 25.0 $^{\circ}$ C.What is the work done by the gas during this expansion?

A) 159 J
B) 125 J
C) 102 J
D) 172 J

Question 18

An ideal gas is in contact with a heat reservoir to that it remains at a constant temperature of 300.0 K.The gas is compressed from 24.0 L to 14.0 L.The mechanical device that operating the piston to compress the gas expends 5.00 kJ of energy.How much heat flows between the gas and the heat reservoir?

A) -3.0 kJ
B) -5.1 kJ
C) -2.0 kJ
D) -5.0 kJ

Question 19

A monatomic ideal gas at 27 $^{\circ}$ C undergoes an isobaric process from A to B followed by an isochoric process from B to C.What is the total work done in these two processes? (A = 2atm,1L; B = 2atm,2L; C = 1atm,2L)

A) 202 J
B) 231 J
C) 187 J
D) 195 J

Question 20

What physical quantity is represented by the area under a curve on a PV diagram where pressure is in Pa and V is in m³?

A) Area in meters²
B) Work in Joules
C) Heat in Watts
D) Heat in Joules
E) Work in Calories

Question 21

An engine delivers 40.0 J of work while it takes in energy from a 400 K thermal source.If the engine discharges energy into a thermal reservoir at 200 K,then what is the least amount of heat needed to run the engine?

A) 55.0 J
B) 65.0 J
C) 80.0 J
D) 110 J

Question 22

A heat pump uses 100 J of work to output 150 J of heat at some temperature.What is the coefficient of performance for the heat pump?

A) 1.0
B) 1.5
C) 2.0
D) 2.5
E) 3.0

Question 23

A heat pump uses 100 J of work output heat at some temperature.If the heat pump withdraws 60 J of heat from some lower temperature,then what is the coefficient of performance for the heat pump?

A) 1.6
B) 2.0
C) 2.4
D) 2.8

Question 24

During an isothermal process,5.0 J of heat is removed from an ideal gas.What is the change in internal energy?

A) zero
B) 2.5 J
C) 5.0 J
D) 10 J

Question 25

A heat engine has an efficiency of 35.0% and receives 150 J of heat per cycle.How much heat does it exhaust in each cycle?

A) zero
B) 52.5 J
C) 97.5 J
D) 150 J

Question 26

During an isothermal process,5.0 J of heat is removed from an ideal gas.What is the work done in the process?

A) zero
B) -5.0 J
C) +5.0 J
D) none of the above

Question 27

A heat engine has an efficiency of 35.0% and its power output is 600 W.What is the rate of heat input?

A) 1.8 kW.
B) 2.0 kW.
C) 2.4 kW.
D) 3.0 kW.

Question 28

In an isochoric process,the internal energy of a system decreases by 50J.What is the heat exchange?

A) zero
B) +50 J
C) -50 J
D) none of the above

Question 29

When the first law of thermodynamics is applied to an ideal gas that is taken through an isothermal process

A) $\Delta$ U = 0.
B) W = 0.
C) Q = 0.
D) none of the above.

Question 30

A refrigerator uses 40.0 J of work to extract 90.0 J from a heat reservoir at 0.00 $^{\circ}$ C.What is the coefficient of performance for the refrigerator?

A) 1.60
B) 2.05
C) 2.25
D) 2.85

Question 31

A engine goes through a cyclic process.During the cyclic process the engine takes in 3200 J of heat and has a heat output of 2400 J.What is the efficiency of the engine?

A) 10%
B) 15%
C) 25%
D) 40%
E) 52%

Question 32

A heat engine has an efficiency of 35.0% and receives 150 J of heat per cycle.How much work does it perform in each cycle?

A) zero
B) 52.5 J
C) 97.5 J
D) 150 J

Question 33

A refrigerator uses 40 J of work to extract heat from a heat reservoir at 0.00 $^{\circ}$ C.If the coefficient of performance of the refrigerator is 2.1,then how much heat is extracted from the heat reservoir at 0.00 $^{\circ}$ C?

A) 48 J
B) 65 J
C) 84 J
D) 90 J

Question 34

In an isochoric process,the internal energy of a system decreases by 50J.What is the work done?

A) zero
B) +50 J
C) -50 J
D) none of the above

Question 35

A heat pump uses 100 J of work to output 150 J of heat at some temperature.What is the heat that is withdrawn from some lower temperature?

A) 90 J
B) 75 J
C) 50 J
D) 25 J

Question 36

A engine goes through a cyclic process.During the cyclic process the engine does 600 J of work and has a heat output of 2400 J.What is the efficiency of the engine?

A) 10%
B) 20%
C) 35%
D) 55%
E) 62%

Question 37

A very efficient engine has the following characteristics - combustion = 1900 $^{\circ}$ C, exhaust = 430 $^{\circ}$ C, 7.0 $\times$ 10⁹ cal of fuel produces 1.4 $\times$ 10⁷ J of work in one hour.What is the output in hp?

A) 5.2 hp
B) 8.1 hp
C) 7.3 hp
D) 6.3 hp

Question 38

An engine takes in 150 J energy from a 400 K thermal source.If the engine discharges energy into a thermal reservoir at 150K,then what is the maximum amount of work one can get out of the engine?

A) 93.8 J
B) 84.2 J
C) 28.5 J
D) 168 J

Question 39

10 joules of heat energy are transferred to a sample of ideal gas at constant volume.As a result,the internal energy of the gas

A) increases by 10 J
B) increases by less than 10 J
C) increases by more than 10 J
D) remains unchanged.

Question 40

A heat pump uses 200 J of work to output 300 J of heat into a heat reservoir at 200 K.What is the coefficient of performance for the heat pump?

A) 1.0
B) 1.5
C) 2.5
D) 2.8

Question 41

A heat pump takes in 60.0 J of energy from a 250 K thermal reservoir outside a house and discharges heat energy into a 350 K thermal reservoir inside a house.What is the minimum amount of work needed to make the pump work?

A) 17.2 J
B) 24.0 J
C) 52.0 J
D) 65.0 J

Question 42

2.00 moles of an ideal gas freely expands from 1.50 liters to 4.00 liters.The change in entropy in the expansion is

A) 5.80 J/K
B) 8.50 J/K
C) 16.3 J/K
D) 18.7 J/K

Question 43

120 J of heat flows by thermal conduction from 100 $^{\circ}$ C to 0.00 $^{\circ}$ C.What is the change in entropy for this process?

A) 0.034 J/K
B) 0.118 J/K
C) 0.201 J/K
D) 0.338 J/K

Question 44

When water freezes,the entropy of the water

A) increases.
B) decreases.
C) does not change.
D) depending on other factors could increase or decrease

Question 45

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

A) entropy remains constant.
B) entropy increases.
C) entropy decreases.
D) depends on the rate of change of the process.

Question 46

When 1.000 kg of ice melts,33.00 $\times$ 10⁴ J/kg of heat are needed.What is the entropy change in the melting process?

A) 758.0 J/K
B) 1,227 J/K
C) 1,684 J/K
D) 2,316 J/K

Question 47

A heat pump takes in energy from a 250 K thermal reservoir outside a house and discharges 140 J of energy into a 350 K thermal reservoir inside a house.What is the minimum amount of work needed to make the pump work?

A) 67.0 J
B) 50.0 J
C) 40.0 J
D) 37.0 J

Question 48

A refrigerator extracts 65 J of heat from a heat reservoir at 0.00 $^{\circ}$ C.If the coefficient of performance of the refrigerator is 2.5,then how much work is needed to run the refrigerator?

A) 26 J
B) 48 J
C) 75 J
D) 90 J

Question 49

A refrigerator extracts 65.0 J of heat from a heat reservoir at 0.00 $^{\circ}$ C.If the coefficient of performance of the refrigerator is 2.50,then how much heat is discharged out of the refrigerator?

A) 125 J
B) 91.0 J
C) 75.0 J
D) 55.0 J

Question 50

A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into the room per cycle.What is the coefficient of performance?

A) 4 J
B) 20 J
C) 24 J
D) 44 J

Question 51

What is the maximum theoretical efficiency possible for an engine operating between 100 $^{\circ}$ C and 400 $^{\circ}$ C?

A) 25%.
B) 45%.
C) 55%.
D) 75%.

Question 52

When 2.000 kg of water evaporates,22.60 $\times$ 10⁵ J/kg of heat are needed.What is the entropy change in the boiling process?

A) 12,120 J/K
B) 8,566 J/K
C) 6,750 J/K
D) 5,844 J/K

Question 53

A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into the room per cycle.How much work is required in each cycle?

A) 4 J
B) 20 J
C) 24 J
D) 44 J

Question 54

One mole of an ideal gas freely expands from 1.00 liter to 2.00 liters.The change in entropy in the expansion is

A) 5.80 J/K
B) 8.50 J/K
C) 16.3 J/K
D) 18.7 J/K

Question 55

A container of ideal gas at STP undergoes an isothermal expansion and its entropy changes by 3.7 J/K.How much work does it do?

A) zero
B) 1.0 $\times$ 10³ J/K
C) -1.0 $\times$ 10³ J/K
D) none of the above.

Question 56

It can be shown that the change in entropy in heating or cooling a sample is given by the relation $\Delta$ S = mc ln (T_F/T_i),where m is the mass of the sample,c is the specific heat of the sample,and T_F and T_i are the final and initial temperatures respectively.What is the change in entropy when 10.0 grams of lead with a specific heat of 0.452 J/gm K is heated from 10.0 $^{\circ}$ C to 50.0 $^{\circ}$ C?

A) 0.45 J/K
B) 0.60 J/K
C) 0.90 J/K
D) 0.30 J/K

Question 57

It can be shown that the change in entropy in heating or cooling a sample is given by the relation $\Delta$ S = mc ln (T_F/T_i),where m is the mass of the sample,c is the specific heat of the sample,and T_F and T_i are the final and initial temperatures respectively.What is the change in entropy when 20.0 grams of aluminum with a specific heat of 0.9 J/gm K is heated from 10.0 $^{\circ}$ C to 60.0 $^{\circ}$ C?

A) +2.93 J/K
B) +2.50 J/K
C) 0 J/K
D) -2.93 J/K

Question 58

It can be shown that the change in entropy in heating or cooling a sample is given by the relation $\Delta$ S = mc ln (T_F/T_i),where m is the mass of the sample,c is the specific heat of the sample,and T_F and T_i are the final and initial temperatures respectively.What is the change in entropy when 20 grams of aluminum with a specific heat of 0.900 J/gm K is cooled from 60.0 $^{\circ}$ C to 10.0 $^{\circ}$ C?

A) +2.93 J/K
B) +2.50 J/K
C) 0.00 J/K
D) -2.93 J/K

Question 59

1.50 moles of an ideal gas freely expands from 1.00 liter to 4.50 liters.The change in entropy in the expansion is

A) 5.80 J/K
B) 8.50 J/K
C) 16.3 J/K
D) 18.7 J/K

Question 60

A refrigerator uses 40.0 J of work to extract heat from a heat reservoir at 0.00 $^{\circ}$
C.If the coefficient of performance of the refrigerator is 2.10,then how much heat is discharged out of the refrigerator at a higher temperature?

A) 52.0 J
B) 66.0 J
C) 86.0 J
D) 124 J

Question 61

Four coins,each with a Head and a Tail,are tossed randomly on to a table.The microstate is defined as the "number of Heads showing".The number of Heads can be,0,1,2,3,4.What value for the "number of Heads showing" has the greatest number of microstates?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 62

A heat pump is used to heat a house in Minnesota in the winter and has half the ideal coefficient of performance for a reversible heat pump.If the outside air temperature is -15 $^{\circ}$ C and the indoor temperature desired is 20 $^{\circ}$ C,and if it can do work at a rate of 1250 W,what is the rate of heat flow into the house?

A) 340 W
B) 1100 W
C) 625 W
D) 300 W

Question 63

An engineer wants to use a river (minimum temperature of 4 $^{\circ}$ C)to cool his electrical plant which heats water with a boiler operating at 220 $^{\circ}$ C.If he wishes to produce 185 kW of power using this plant,what is the minimum energy he must supply to his boiler if it is maximally efficient?

A) 233 kW
B) 187 kW
C) 332 kW
D) 418 kW

Question 64

On a PV diagram representing an isothermal compression,what is the relationship between the initial P value and the final P value?

A) The initial is greater than the final
B) The initial is less than the final
C) They may be either - it depends on the temperature of the process
D) They may be the same.

Question 65

A system in a certain macro state has 1.2 $\times$ 10³ microstates.Through some process,the system changes the number of microstates to 3 $\times$ 10⁴.What is the change in entropy for the process?

A) 1.1 $\times$ 10^-23 J/K
B) 2.1 $\times$ 10^-23 J/K
C) 4.4 $\times$ 10^-23 J/K
D) 5.6 $\times$ 10^-23 J/K

Question 66

A heat pump is used to heat a house in Minnesota in the winter and has half the ideal coefficient of performance for a reversible heat pump.If the outside air temperature is -15 $^{\circ}$ C and the indoor temperature desired is 20 $^{\circ}$ C,what is its coefficient of performance under these conditions?

A) 3.7
B) 1.1
C) 2.0
D) 4.2

Question 67

An refrigerator keeps food in the freezer portion at -15 $^{\circ}$ C and dumps excess heat into the kitchen,whose temperature is 20 $^{\circ}$ C.If the refrigerator has half the coefficient of performance of an ideal reversible refrigerator,what is the refrigerator's coefficient of performance under these conditions?

A) 1.1
B) 4.2
C) 2.0
D) 3.7

Question 68

For a system undergoing an isothermal process,

A) $\Delta$ Q = - $\Delta$ U
B) $\Delta$ Q = 0
C) $\Delta$ Q = $\Delta$ U
D) $\Delta$ Q = -W
E) $\Delta$ Q = W

Question 69

An ideal,reversible refrigerator keeps food in the freezer portion at -15 $^{\circ}$ C and dumps excess heat into the kitchen,whose temperature is 20 $^{\circ}$ C.What is the refrigerator's coefficient of performance under these conditions?

A) 7.4
B) 4.0
C) 8.4
D) 2.1

Question 70

An engineer uses a river (which averages 4 $^{\circ}$ C)to cool his electrical plant which heats water with a boiler operating at 750 $^{\circ}$ C .What's the maximal performance (in terms of efficiency)theoretically possible for this electrical plant?

A) 64%
B) 36%
C) 27%
D) 73%

Question 71

For a system undergoing an adiabatic process,

A) $\Delta$ Q = $\Delta$ U
B) $\Delta$ Q = - $\Delta$ U
C) $\Delta$ Q = -W
D) $\Delta$ Q = 0
E) $\Delta$ Q = W

Question 72

For a system undergoing an isothermal expansion,the work done on the working fluid is:

A) May be either,depending on the temperature
B) Positive
C) Zero
D) Negative

Question 73

A friend tells you that he knows of a situation in heat passed from one body in thermal contact with another body whose temperature was higher than that of the first.He explains that he thinks the 2^nd law of thermodynamics must have been violated.Is he correct?

A) No. If the temperature difference is small enough,heat can spontaneously flow from the cooler to the hotter body.
B) Yes. Heat cannot pass from one body to a hotter body.
C) No. He forgot that if external work is done on the system this is possible.
D) No. The cooler body can give up energy to the hotter body by radioactivity or another natural process.

Question 74

100 coins,each with a Head and a Tail,are tossed randomly onto a table.A microstate is defined as the number of Heads that appear after the toss.What is the value for the number of Heads that has the most number of microstates?

A) 95
B) 75
C) 60
D) 50

Question 75

An refrigerator keeps food in the freezer portion at -15 $^{\circ}$ C and dumps excess heat into the kitchen,whose temperature is 22 $^{\circ}$ C.If the refrigerator has half the coefficient of performance of an ideal reversible refrigerator,and if its motor can supply 250W of power,what is the rate of heat flow out of the freezer portion of the refrigerator?

A) 340W
B) 300W
C) 1100W
D) 625W

Question 76

A system in a certain macro state has 2 $\times$ 10²³ microstates.Through some process,the system changes the number of microstates to 3 $\times$ 10²³.What is the change in entropy for the process?

A) 2.5 $\times$ 10²³ J/K
B) 1.2 $\times$ 10¹³ J/K
C) 4.2 $\times$ 10^-10 J/K
D) 5.6 $\times$ 10^-24 J/K

Question 77

Two coins,each with a Head and a Tail,are tossed randomly onto a table.The microstate is defined as the "number of Heads showing".The number of Heads can be,0,1,2.What value for the "number of Heads showing" has the greatest number of microstates?

A) 0
B) 1
C) 2

Question 78

A friend tells you that he knows of a situation in which bowl of ice sitting by itself on a table in a room whose air temperature is 20 $^{\circ}$ C gives up heat the surrounding air.What's wrong with this concept?

A) It would violate the 0^th law of thermodynamics
B) It would violate the 1^st law of thermodynamics
C) It would violate the 2^nd law of thermodynamics
D) It would violate the 3^rd law of thermodynamics

Question 79

An engineer uses a river (minimum temperature of 4 $^{\circ}$ C)to cool his electrical plant which heats water with a boiler operating at 220 $^{\circ}$ C.His boiler uses 420 kW of energy to heat water to steam.What is the maximum power output under ideal circumstances?

A) 230 kW
B) 186 kW
C) 330 kW
D) 416 kW

Question 80

An ideal reversible heat pump is used to heat a house in Minnesota in the winter.If the outside air temperature is -15 $^{\circ}$ C and the indoor temperature desired is 20 $^{\circ}$ C,what is the expected coefficient of performance for the heat pump under these conditions?

A) 2.1
B) 8.4
C) 7.4
D) 4.0