Question 1

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 the area is given by the product of the change in volume and the pressure, which is the definition of the work done by a gas. Therefore, the correct answer is C) work.

Question 2

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 3

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

Accepted Answer

A Carnot engine has the highest theoretical efficiency among all heat engines. It operates between two constant temperature reservoirs and reversibly converts heat into work. Both Hero's engine and internal combustion engines (gasoline and diesel) have lower efficiencies due to various factors such as friction, combustion inefficiencies, and heat losses.

Question 4

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 ice melts, it transitions from a solid state to a liquid state, which increases its entropy. Therefore, the system undergoes an increase in entropy.

Question 5

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 the formula:
efficiency = 1 - (T2/T1),
where T1 is the temperature of the hot reservoir and T2 is the temperature of the cold reservoir. Converting the temperatures to Kelvin, we get T1 = 373 K and T2 = 273 K. Plugging these values into the efficiency formula, we get efficiency = 1 - (273/373) = 0.27 or 27%. Therefore, the correct answer is C.

Question 6

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:

Accepted Answer

The thermal pollution is related to the waste heat rejected to the low-temperature reservoir. The efficiency of a Carnot engine is given by 1 - (T_cold/T_hot). A higher efficiency means less waste heat. On Day One, with a lower hot reservoir temperature (500 K), the efficiency is lower compared to Day Two (600 K), resulting in more waste heat and thus greater thermal pollution on Day One.

Question 7

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?

Accepted Answer

The change in entropy of the universe is equal to the change in entropy of the avalanche plus the change in entropy of the surroundings. The change in entropy of the avalanche is given by:$$\Delta S_{avalanche} = m c_p \ln \left(\frac{T_f}{T_i}\right)$$where m is the mass of the avalanche, c_p is the specific heat of ice, T_f is the final temperature of the avalanche, and T_i is the initial temperature of the avalanche.The change in entropy of the surroundings is given by:$$\Delta S_{surroundings} = -\frac{Q}{T}$$where Q is the heat transferred from the avalanche to the surroundings and T is the temperature of the surroundings.In this case, the final temperature of the avalanche is 0°C and the initial temperature of the avalanche is -1°C. The specific heat of ice is 2.09 J/g°C. The mass of the avalanche is 2500 kg. The heat transferred from the avalanche to the surroundings is:$$Q = m c_p (T_f - T_i) = (2500 kg)(2.09 J/g°C)(0°C - (-1°C)) = 5225 J$$The temperature of the surroundings is 0°C. Therefore, the change in entropy of the surroundings is:$$\Delta S_{surroundings} = -\frac{Q}{T} = -\frac{5225 J}{273 K} = -19.1 J/K$$The change in entropy of the universe is:$$\Delta S_{universe} = \Delta S_{avalanche} + \Delta S_{surroundings} = (14000 J/K) + (-19.1 J/K) = 13980.9 J/K$$Therefore, the correct answer is A.

Question 8

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)

Accepted Answer

The answer of When gasoline is burned, it gives off...

Question 9

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 energy cannot be created or destroyed, only transferred or converted from one form to another. This law does not make any statement about the entropy of an isolated system, which is determined by the second law of thermodynamics. Therefore, none of the choices mentioned are applicable to the first law of thermodynamics.

Question 10

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 the heat engine is positive when the path around the area proceeds in a clockwise fashion. This is because work is done when the volume of the gas decreases (isobaric compression) and when the pressure of the gas increases (isochoric heating). In a clockwise cycle, the gas undergoes both of these processes. Therefore, the area enclosed in the P-V diagram represents positive work.

Question 11

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?

Accepted Answer

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

Question 12

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)

Accepted Answer

The change in entropy is given by:$$\Delta S = \frac{L_v}{T}$$where:* $L_v$ is the latent heat of vaporization* $T$ is the temperaturePlugging in the given values, we get:$$\Delta S = \frac{2.26 	imes 10^6 	ext{ J/kg}}{373 	ext{ K}} = 6060 	ext{ J/K}$$

Question 13

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 14

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 states that the entropy of an isolated system always increases or remains constant. Therefore, choice C, entropy increases, is the most appropriate answer.

Question 15

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.)

Accepted Answer

The change in entropy (ΔS) is calculated using the formula ΔS = Q/T, where Q is the heat absorbed and T is the temperature in Kelvin. First, convert the heat of fusion to J/mole: 8.82 x 10^4 J/kg * 108 g/mole * (1 kg/1000 g) = 9525.6 J/mole. For two moles, Q = 2 * 9525.6 J = 19051.2 J. Convert 961°C to Kelvin: 961 + 273.15 = 1234.15 K. ΔS = 19051.2 J / 1234.15 K = 15.4 J/K.

Question 16

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

An increase in orderliness or organization indicates a decrease in entropy.

Question 17

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 the expression (1 - T_c/T_h). Therefore, decreasing the temperature of the cold reservoir (option C) would have the greatest impact on the efficiency because the denominator would be smaller, thereby increasing the ratio and the efficiency. Increasing the temperature of the hot reservoir (option A) or the cold reservoir (option B) would have a smaller impact on the efficiency since the difference in temperatures would still be the same, and the ratio would not change significantly. Therefore, option C is the best choice.

Question 18

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

Accepted Answer

The appropriate unit for measuring entropy changes is J/K, since entropy is a measure of the degree of disorder in a system and is related to the amount of thermal energy that is unavailable to do work. The change in entropy (∆S) is defined as ∆S = Q/T, where Q is the heat transferred and T is the temperature at which the heat transfer occurs. Therefore, the units for entropy change must be in J/K. Choices A and B are not appropriate units for measuring entropy changes, as they do not account for temperature. Choice C is a unit for measuring power (rate of energy transfer) and is not appropriate for measuring entropy changes.

Question 19

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

Accepted Answer

In a refrigerator, heat is transferred from the cooler interior (where the food is stored) to the warmer exterior environment. This process is made possible by the refrigerator's cooling system, which uses a refrigerant and a cycle of evaporation and condensation to remove heat from the inside of the refrigerator and expel it outside, thus going against the natural direction of heat flow from hot to cold.

Question 20

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?

Accepted Answer

The answer of A 600-MW electric power plant has an...

Quiz 16: Thermodynamics

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

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)

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

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

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?

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)

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 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?

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)

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?

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.)

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 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?

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

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

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?

Quiz 16: Thermodynamics

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

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)

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

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

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?

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)

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 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?

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, Lv = 2.26 * 106 J/kg)

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?

What is the change in entropy ( Δ\DeltaΔ 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.)

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 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?

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

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

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

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 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?

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)

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

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 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?