Question 1

A company that produces pulsed gas heaters claims their efficiency is approximately 90%.If an engine operates between 250°C and 25°C,what is its maximum thermodynamic efficiency?

Accepted Answer

A) 83% 
B) 65% 
C) 43% 
D) 90% 
E) 56%

Question 2

What is the probability of rolling either a 7 or 11 on a single roll of a pair of dice?

Accepted Answer

A) 1/6 
B) 2/9 
C) 3/8 
D) 1/3 
E) 1/2

Question 3

For the same temperature increase in a system,the change in entropy,ΔS,is largest in a reversible

Accepted Answer

A) constant volume process. 
B) constant pressure process. 
C) adiabatic process. 
D) process in which no heat is transferred. 
E) process in which no work is performed.

Question 4

A gasoline engine absorbs 2 500 J of heat at 250°C and expels 2 000 J at a temperature of 50°C.The magnitude of the change in entropy (in J/K)for the system is

Accepted Answer

A) 6.2 
B) 4.7 
C) 1.4 
D) 10.9 
E) 3.2

Question 5

One kilogram of chilled water (0°C)is placed in a freezer which is kept at 0°F (−18°C).Approximately how much electric energy (in kilocalories)is needed just to freeze the water if the room temperature is maintained at 75°F (24°C)? (Lice = 333 J/g;cice = 209 J/g⋅°C. )

Accepted Answer

A) 11 
B) 15 
C) 16 
D) 13 
E) 33

Question 6

An ideal heat engine can have an efficiency of 1 if the temperature of the low temperature reservoir is

Accepted Answer

A) 0 K. 
B) 0°C. 
C) 0°F. 
D) 0°R. 
E) the same as the temperature of the heat source.

Question 7

A 4.00-liter container is divided into two equal parts,one part containing 0.0100 mole of neon,and the other part containing 0.0100 mole of helium.The divider is removed and the gases mix.What is the change in entropy (in J/K)of this system?

Accepted Answer

A) 0.057 6 
B) 0.115 
C) 0.173 
D) 0.086 4 
E) 0.144

Question 8

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Qc/Qh,we can calculate

Accepted Answer

A) n,the number of moles of the ideal gas. 
B) the ratio Vc/Vh of the volumes of the ideal gas. 
C) the ratio Pc/Ph of the pressures of the ideal gas. 
D) the ratio PcVc/PhVh of the products of volumes and pressures of the ideal gas. 
E) the value of Avogadro's number.

Question 9

A steam engine is operating at its theoretical maximum efficiency of 60%.If the waste heat has a temperature of 100°F (38°C),what is the temperature of the boiler?

Accepted Answer

A) 350°C 
B) 94°C 
C) 225°C 
D) 504°C 
E) 775°C

Question 10

For a pair of dice,how many microstates are there that result in the macrostate of rolling a 7?

Accepted Answer

A) 1 
B) 5 
C) 6 
D) 7 
E) 36

Question 11

In a nuclear power plant,the reactor produces 500°C steam that is used to power the steam turbines which generate 1 500 MW of electrical power.The cooling tower eliminates the waste heat at 50°C.If the efficiency of the plant were that of a Carnot engine,at what rate would waste heat be vented to the atmosphere?

Accepted Answer

The answer of In a nuclear power plant,the reactor produces...

Question 12

A refrigerator has a coefficient of performance of 4.If the refrigerator absorbs 30 cal of heat from the cold reservoir in each cycle,the heat expelled (in cal)into the heat reservoir is

Accepted Answer

A) 40.5 
B) 37.5 
C) 36.5 
D) 34.5 
E) 22.5

Question 13

Find the change in entropy (in J/K)when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm3 to a final volume of 100 cm3.

Accepted Answer

A) 167 
B) 100 
C) 67 
D) 52 
E) 152

Question 14

Since Lice = 333 J/g,the change in entropy (in cal/K)when 1.00 kg of ice melts is

Accepted Answer

A) 144 
B) 291 
C) 312 
D) 516 
E) 80

Question 15

Which answer below is not a statement of the second law of thermodynamics?

Accepted Answer

A) Real processes proceed in a preferred direction. 
B) Energy does not flow spontaneously by heat from a cold to a hot reservoir. 
C) The entropy of the universe increases in all natural processes. 
D) In theory,heat engines working in a cycle employ reversible processes. 
E) You cannot construct a heat engine,operating in a cycle that does nothing but take heat from a reservoir and perform an equal amount of work.

Question 16

One kilogram of chilled water at 32°F (0°C)is placed in a freezer which is kept at 0°F (−18°C).Approximately how much electric energy (in kilocalories)is needed to operate the compressor to cool this water to 0°F if the room temperature is maintained at 75°F (24°C)? (Lice = 3.33 × 105 J/kg;cice = 2.09 × 103 J/kg⋅°C)

Accepted Answer

A) 13 
B) 1.5 
C) 15 
D) 16 
E) 33

Question 17

The change in entropy of a mass m of a solid substance which has a latent heat of fusion L and melts at a temperature T is

Accepted Answer

A) LT/m 
B) mL ln(T) 
C) mLT 
D) mL/T 
E) L/mT

Question 18

A violation of the second law of thermodynamics would occur if

Accepted Answer

A) a ball lying on the ground started to bounce. 
B) transfer of energy by heat moved energy from an object at low temperature to an object at a higher temperature. 
C) a refrigerator heated the air in the room in which the refrigerator is located. 
D) any of the above occurred. 
E) (a)or (b)occurred,but not (c).

Question 19

100 grams of molten lead (600°C)is used to make musket balls.If the lead shot is allowed to cool to room temperature (21°C),what is the change in entropy (in J/K)of the lead? (For the specific heat of molten and solid lead use 1.29 J/g⋅°C;the latent heat of fusion and the melting point of lead are 2.45 × 104 J/kg and 327°C. )

Accepted Answer

A) −145 
B) −252 
C) −302 
D) −429 
E) −100

Question 20

A homeowner has a new oil furnace which has an efficiency of 60%.For every 100 barrels of oil needed to heat his house,how much (in barrels of oil)goes up the chimney as waste heat?

Accepted Answer

A) 20 
B) 60 
C) 40 
D) 80 
E) 10

Exam 22: Heat Engines, entropy, and the Second Law of Thermodynamics

A company that produces pulsed gas heaters claims their efficiency is approximately 90%.If an engine operates between 250°C and 25°C,what is its maximum thermodynamic efficiency?

What is the probability of rolling either a 7 or 11 on a single roll of a pair of dice?

For the same temperature increase in a system,the change in entropy,ΔS,is largest in a reversible

A gasoline engine absorbs 2 500 J of heat at 250°C and expels 2 000 J at a temperature of 50°C.The magnitude of the change in entropy (in J/K) for the system is

One kilogram of chilled water (0°C) is placed in a freezer which is kept at 0°F (−18°C) .Approximately how much electric energy (in kilocalories) is needed just to freeze the water if the room temperature is maintained at 75°F (24°C) ? (L_ice = 333 J/g;c_ice = 209 J/g⋅°C. )

An ideal heat engine can have an efficiency of 1 if the temperature of the low temperature reservoir is

A 4.00-liter container is divided into two equal parts,one part containing 0.0100 mole of neon,and the other part containing 0.0100 mole of helium.The divider is removed and the gases mix.What is the change in entropy (in J/K) of this system?

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Q_c/Q_h,we can calculate

A steam engine is operating at its theoretical maximum efficiency of 60%.If the waste heat has a temperature of 100°F (38°C) ,what is the temperature of the boiler?

For a pair of dice,how many microstates are there that result in the macrostate of rolling a 7?

A refrigerator has a coefficient of performance of 4.If the refrigerator absorbs 30 cal of heat from the cold reservoir in each cycle,the heat expelled (in cal) into the heat reservoir is

Find the change in entropy (in J/K) when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm³ to a final volume of 100 cm³.

Since L_ice = 333 J/g,the change in entropy (in cal/K) when 1.00 kg of ice melts is

Which answer below is not a statement of the second law of thermodynamics?

The change in entropy of a mass m of a solid substance which has a latent heat of fusion L and melts at a temperature T is

A violation of the second law of thermodynamics would occur if

A homeowner has a new oil furnace which has an efficiency of 60%.For every 100 barrels of oil needed to heat his house,how much (in barrels of oil) goes up the chimney as waste heat?

Exam 22: Heat Engines, entropy, and the Second Law of Thermodynamics

A company that produces pulsed gas heaters claims their efficiency is approximately 90%.If an engine operates between 250°C and 25°C,what is its maximum thermodynamic efficiency?

What is the probability of rolling either a 7 or 11 on a single roll of a pair of dice?

For the same temperature increase in a system,the change in entropy,ΔS,is largest in a reversible

A gasoline engine absorbs 2 500 J of heat at 250°C and expels 2 000 J at a temperature of 50°C.The magnitude of the change in entropy (in J/K) for the system is

One kilogram of chilled water (0°C) is placed in a freezer which is kept at 0°F (−18°C) .Approximately how much electric energy (in kilocalories) is needed just to freeze the water if the room temperature is maintained at 75°F (24°C) ? (Lice = 333 J/g;cice = 209 J/g⋅°C. )

An ideal heat engine can have an efficiency of 1 if the temperature of the low temperature reservoir is

A 4.00-liter container is divided into two equal parts,one part containing 0.0100 mole of neon,and the other part containing 0.0100 mole of helium.The divider is removed and the gases mix.What is the change in entropy (in J/K) of this system?

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Qc/Qh,we can calculate

A steam engine is operating at its theoretical maximum efficiency of 60%.If the waste heat has a temperature of 100°F (38°C) ,what is the temperature of the boiler?

For a pair of dice,how many microstates are there that result in the macrostate of rolling a 7?

A refrigerator has a coefficient of performance of 4.If the refrigerator absorbs 30 cal of heat from the cold reservoir in each cycle,the heat expelled (in cal) into the heat reservoir is

Find the change in entropy (in J/K) when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm3 to a final volume of 100 cm3.

Since Lice = 333 J/g,the change in entropy (in cal/K) when 1.00 kg of ice melts is

Which answer below is not a statement of the second law of thermodynamics?

The change in entropy of a mass m of a solid substance which has a latent heat of fusion L and melts at a temperature T is

A violation of the second law of thermodynamics would occur if

A homeowner has a new oil furnace which has an efficiency of 60%.For every 100 barrels of oil needed to heat his house,how much (in barrels of oil) goes up the chimney as waste heat?

One kilogram of chilled water (0°C) is placed in a freezer which is kept at 0°F (−18°C) .Approximately how much electric energy (in kilocalories) is needed just to freeze the water if the room temperature is maintained at 75°F (24°C) ? (L_ice = 333 J/g;c_ice = 209 J/g⋅°C. )

By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Q_c/Q_h,we can calculate

Find the change in entropy (in J/K) when 5.00 moles of an ideal monatomic gas are allowed to expand isobarically from an initial volume of 20 cm³ to a final volume of 100 cm³.

Since L_ice = 333 J/g,the change in entropy (in cal/K) when 1.00 kg of ice melts is