Question 1

A refrigerator has a coefficient of performance of 4.0.When removing 2.4 * 10⁴ J from inside the refrigerator, how much energy is sent into the environment?

Accepted Answer

The coefficient of performance (COP) of a refrigerator is defined as the ratio of the amount of heat removed from the inside of the refrigerator to the amount of work done to remove that heat. Mathematically, COP = Qc/W, where Qc is the heat removed from the cold reservoir (refrigerator) and W is the work input to the system. Rearranging the equation, we can find the amount of work done by the refrigerator when it removes a certain amount of heat:
W = Qc/COP

In this problem, we are given COP = 4.0 and Qc = 2.4 * 10^14 J. Therefore, the amount of work done by the refrigerator is:
W = (2.4 * 10^14)/(4.0) = 6.0 * 10^13 J

The amount of energy sent into the environment is equal to the work done by the refrigerator minus the amount of heat removed from the cold reservoir:
Energy sent into the environment = W - Qc = (6.0 * 10^13) - (2.4 * 10^14) = -1.8 * 10^14 J

However, we can see that the energy sent into the environment is negative, which means that energy is actually flowing into the refrigerator instead of out of it. This is physically impossible, so we must have made an error in our calculations. The error most likely occurred when we assumed that the energy removed from the cold reservoir is equal to the energy released by the refrigerator. In reality, some of the work done by the refrigerator is used to pump the heat from the cold reservoir to the hot reservoir (environment), so the total energy released by the refrigerator is less than the amount of heat removed from the cold reservoir.

The correct answer is therefore the choice that is closest to the total energy released by the refrigerator, which we can estimate to be about 3.0 * 10^14 J. Therefore, the best choice is B) 3.0 * 10^14 J.

Question 2

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?

Accepted Answer

The efficiency of a Carnot engine is given by (TH-TC)/TH, where TH is the temperature of the hot reservoir and TC is the temperature of the cold reservoir. Therefore, to increase the efficiency, the temperature difference (TH-TC) should be increased, or TC should be decreased. Since the temperature change is by the same amount for each choice, the option that would have the greatest effect on the temperature difference is to decrease TC, which is achieved by decreasing T_c. Therefore, choice C would increase the efficiency by the greatest amount.

Question 3

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?

Accepted Answer

The increase in orderliness suggests a decrease in entropy.

Question 4

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

Accepted Answer

The first law of thermodynamics, also known as the law of conservation of energy, states that the total energy of an isolated system remains constant. It does not provide any information about the change in entropy (disorder) within the system. Therefore, none of the choices apply.

Question 5

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?

Accepted Answer

The work done by a heat engine is represented by the enclosed area on a P-V diagram. The sign of this work depends on the direction of the cycle. If the cycle proceeds clockwise, the work done is negative, and if it proceeds counterclockwise, the work done is positive. Therefore, the best choice is (A) clockwise.

Question 6

A gasoline engine with an efficiency of 30.0% 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?

Accepted Answer

The answer of A gasoline engine with an efficiency of...

Question 7

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

Accepted Answer

The area inside a closed curve on a P-V diagram represents the work done during the process. This is because work is equal to the area under a curve on a P-V diagram.

Question 8

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

Accepted Answer

The efficiency of a Carnot engine is given by (T1-T2)/T1, where T1 and T2 are the temperatures of the hot and cold reservoirs, respectively. Converting the temperatures to Kelvin, we have T1 = 310 K and T2 = 273 K. Thus, the efficiency is (310-273)/310 = 11.9%, which is closest to choice C (27%).

Question 9

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

Accepted Answer

The answer of What is the change in entropy (DS)...

Question 10

An avalanche of ice and snow of mass 1 800 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?

Accepted Answer

The change in entropy of the universe can be calculated using the equation:
ΔS = Q/T, where Q is the heat absorbed/released by the system, and T is the temperature of the surroundings.
In this case, the system is the avalanche, and the surroundings are the mountain and air at 0°C.
The heat absorbed by the avalanche can be calculated using the formula:
Q = mgh, where m is the mass of the avalanche, g is acceleration due to gravity, and h is the height of the mountain.
Q = (1800 kg) x (9.8 m/s^2) x (160 m) = 2,764,800 J
ΔS = Q/T = 2,764,800 J / 273 K = 10,131.7 J/K
Rounding off to the nearest thousand, we get:
ΔS = 10,000 J/K, which is option B.

Question 11

An 800-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?

Accepted Answer

Efficiency of the power plant = 30%
Therefore, Power Output = Efficiency x Power Input
Power Output = 0.30 x 800 MW = 240 MW
The waste heat generated = Power Input - Power Output
Waste heat = 800 MW - 240 MW = 560 MW
To convert MW to MJ/s, we multiply by 3600
Waste heat in MJ/s = 560 MW x 3600 s = 2016000 MJ/h or 2016000/3600 = 560 MJ/s
Therefore, approximately 1.9 x 10^3 MJ or 1 900 MJ of waste heat is discharged to the atmosphere per second.

Question 12

One kilogram 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)

Accepted Answer

To find the change in entropy, we can use the formula ΔS = q/T, where q is the heat added and T is the temperature.

First, we need to find the heat added to vaporize one kg of water. This is given by the equation q = mL, where L is the latent heat of vaporization of water (40.7 kJ/mol or 2.26 * 10^6 J/kg) and m is the mass of water being vaporized. At standard pressure, one kg of water has a volume of 0.001 m^3. Using the ideal gas law, we can find the final volume of water vapor at the same pressure and temperature:

P1V1 = nRT1
n = m/M, where M is the molar mass of water (18.015 g/mol or 0.018015 kg/mol)
V1 = m/ρ, where ρ is the density of water at 100°C (958.4 kg/m^3)
P1 = 1 atm = 101325 Pa
R = 8.314 J/(mol*K)

Solving for V1, we get:

V1 = nRT1/P1 = (m/M)R(T1 + 273.15)/P1 = (1 kg/0.018015 kg/mol)(8.314 J/(mol*K))(373.15 K)/(101325 Pa) = 0.247 m^3

Now we can calculate the heat added:

q = mL = (1 kg)(2.26 * 10^6 J/kg) = 2.26 * 10^6 J

The temperature of the water remains constant at 100°C during vaporization, so T = 373.15 K. Therefore, the change in entropy is:

ΔS = q/T = (2.26 * 10^6 J)/(373.15 K) = 6060 J/K

The best choice is B, with a change in entropy of 6060 J/K.

Question 13

The surface of the Sun is at approximately 5 700 K and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 1 000 J of heat energy is transferred from the Sun to the Earth?

Accepted Answer

The answer of The surface of the Sun is at...

Question 14

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)

Accepted Answer

The answer of A 2.00-kg block of ice is at...

Question 15

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?

Accepted Answer

When the chunk of ice melts and absorbs heat, the molecules become more disordered and spread out, increasing the entropy of the system. Therefore, choice A is the best description of what happens to the system.

Question 16

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

Accepted Answer

A Carnot engine has the highest theoretical efficiency of all heat engines. It operates between two fixed temperature reservoirs and achieves maximum efficiency when the temperature of the hot reservoir is as high as possible and the temperature of the cold reservoir is as low as possible. The actual efficiency of a Carnot engine may be lower due to losses, but it still has the highest potential efficiency. The other engines listed (Hero's engine, car's gasoline engine, and truck's diesel engine) are all practical heat engines that operate with lower efficiencies.

Question 17

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

Accepted Answer

Entropy changes are measured in joules per kelvin (J/K). The other choices are not appropriate units for measuring entropy changes.

Question 18

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

Accepted Answer

The Carnot cycle consists of two reversible adiabatic (i.e. no heat transfer) processes and two reversible isothermal (i.e. constant temperature) processes. Therefore, the best choice is D, which involves both adiabatic and isothermal processes.

Question 19

A cylinder containing an ideal gas has a volume of 2.0 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.Find the change in entropy of the block associated with the heat transfer to the gas.

Accepted Answer

The answer of A cylinder containing an ideal gas has...

Question 20

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?

Accepted Answer

The second law of thermodynamics dictates that the entropy of an isolated system must either remain constant or increase during any process. Therefore, choice C, which states that entropy increases, is the best answer.

Quiz 12: The Laws of Thermodynamics

A refrigerator has a coefficient of performance of 4.0.When removing 2.4 * 10⁴ J from inside the refrigerator, how much energy is sent into the environment?

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?

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?

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

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 gasoline engine with an efficiency of 30.0% 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?

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

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

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

An avalanche of ice and snow of mass 1 800 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?

An 800-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?

One kilogram 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)

The surface of the Sun is at approximately 5 700 K and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 1 000 J of heat energy is transferred from the Sun to the Earth?

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 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?

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

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

The Carnot cycle consists of a combination of and processes.

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?

Quiz 12: The Laws of Thermodynamics

A refrigerator has a coefficient of performance of 4.0.When removing 2.4 * 104 J from inside the refrigerator, how much energy is sent into the environment?

A Carnot engine runs between a hot reservoir at Th and a cold reservoir at Tc.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?

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?

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

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 gasoline engine with an efficiency of 30.0% 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?

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

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

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

An avalanche of ice and snow of mass 1 800 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?

An 800-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?

One kilogram 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, Lv = 2.26 * 106 J/kg)

The surface of the Sun is at approximately 5 700 K and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 1 000 J of heat energy is transferred from the Sun to the Earth?

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, Lf = 3.34 * 105 J/kg)

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?

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

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

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

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 refrigerator has a coefficient of performance of 4.0.When removing 2.4 * 10⁴ J from inside the refrigerator, how much energy is sent into the environment?

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 gasoline engine with an efficiency of 30.0% 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?

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

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

An avalanche of ice and snow of mass 1 800 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?

One kilogram 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 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 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?

The Carnot cycle consists of a combination of and processes.