Question 1

When a gas expands adiabatically,

Accepted Answer

Adiabatic expansion implies that there is no heat exchange with surroundings. Since there is no energy transfer in the form of heat, the internal (thermal) energy of the gas must decrease in order to conserve energy. This is in accordance with the first law of thermodynamics, which states that the change in internal energy of a system is equal to the work done on the system plus the heat transferred to the system. Since no heat is transferred, the decrease in internal energy must be due to work done on the system, which causes the gas to expand.

Question 2

A certain gas is compressed adiabatically.The amount of work done on the gas is 800 J.What is the change in the internal (thermal)energy of the gas?

Accepted Answer

In an adiabatic process, there is no heat exchange with the surroundings. Therefore, the work done on the gas directly increases its internal energy by the same amount, which is 800 J.

Question 3

The process shown on the pV diagram in the figure is an

Accepted Answer

D

Question 4

A certain ideal gas has a molar specific heat at constant volume 7R/2.What is its molar specific heat at constant pressure?

Accepted Answer

The relationship between the molar specific heat at constant volume and constant pressure for an ideal gas is given by:
Cp - Cv = R
Where Cp is the molar specific heat at constant pressure, Cv is the molar specific heat at constant volume, and R is the gas constant.
Substituting Cv = 7R/2, we get:
Cp - 7R/2 = R
Solving for Cp, we get:
Cp = 9R/2

Question 5

The second law of thermodynamics leads us to conclude that

Accepted Answer

The second law of thermodynamics states that the total entropy (or disorder) of a closed system will always increase over time, leading to a gradual increase in disorder in the universe. This means that the energy available to do work decreases over time, and it becomes increasingly difficult to convert heat into work. Therefore, choice B is the correct answer. The other choices are incorrect because they contradict the second law (A) or are not related to the second law (C, D, E).

Question 6

In a given reversible process,the temperature of an ideal gas is kept constant as the gas is compressed to a smaller volume.Which one of the following statements about the gas is correct?

Accepted Answer

As the temperature of the gas is kept constant during the compression process, the gas cannot absorb energy in the form of heat from its surroundings. Therefore, it must release energy in the form of heat to its surroundings. This energy release is necessary to maintain a constant temperature while the gas is being compressed. Choice A is incorrect for this reason. Choice C is also incorrect, as the pressure of the gas is increasing due to the compression process. Choice D is incorrect, as the process is not adiabatic if heat energy is being transferred between the gas and its surroundings. Choice E is not correct, as the information provided is sufficient to make a determination about the behavior of the gas during this process.

Question 7

Which one of the following is a true statement?

Accepted Answer

A) The second law of thermodynamics is not a consequence of the first law; it is an independent principle stating that the total entropy of an isolated system can never decrease over time. B) Heat flows spontaneously from a hot body to a cold one, not the reverse, regardless of the process's reversibility. C) It is possible to convert work entirely into heat through processes like friction. D) It is possible to transfer heat from a cooler to a hotter body using external work, as in a refrigerator. Therefore, all given statements are false.

Question 8

Which of the following is a false statement?

Accepted Answer

Entropy in an isolated system does not remain constant; it increases over time according to the second law of thermodynamics.

Question 9

A certain ideal gas has a molar specific heat at constant pressure of 33.2 J/mol ∙ K.Its molar specific heat at constant volume is closest to which of the following values? (R = 8.31J/mol ∙ K)

Accepted Answer

For an ideal gas, we have the relationship between the molar specific heats as follows:
Cp - Cv = R
where Cp and Cv are the molar specific heats at constant pressure and volume, respectively.
Substituting the given value of Cp and R, we get:
33.2 J/mol ∙ K - Cv = 8.31 J/mol ∙ K
Solving for Cv, we get:
Cv = 33.2 J/mol ∙ K - 8.31 J/mol ∙ K ≈ 24.9 J/mol ∙ K
Therefore, the closest value among the given choices is D.

Question 10

For an ideal gas,

Accepted Answer

The answer of For an ideal gas,
...

Question 11

A certain ideal gas has a molar specific heat at constant pressure of 7R/2.What is its molar specific heat at constant volume?

Accepted Answer

The relationship between the molar specific heat at constant pressure (Cp) and the molar specific heat at constant volume (Cv) for an ideal gas is given by Cp - Cv = R. Given Cp = 7R/2, substituting into the equation gives 7R/2 - Cv = R, solving for Cv gives Cv = 5R/2.

Question 12

An ideal gas undergoes an isothermal expansion.During this process,its entropy

Accepted Answer

During an isothermal expansion, the temperature remains constant. As the volume of the gas increases, the number of microstates available to the gas molecules increases, allowing for a greater number of possible arrangements of the molecules. This leads to an increase in entropy, so the correct choice is (C) increases.

Question 13

An ideal gas is compressed isobarically to one-third of its initial volume.The resulting pressure will be

Accepted Answer

The pressure remains constant during an isobaric process, so compressing the gas to one-third of its initial volume does not change the pressure.

Question 14

For an ideal gas,

Accepted Answer

For an ideal gas, C_P > C_V for all ideal gases because C_P includes both translational and rotational energy, while C_V includes only translational energy.

Question 15

The process shown on the TV graph in the figure is an

Accepted Answer

The answer of The process shown on the TV graph...

Question 16

A 10-L flask and a 1-L flask each contain two moles of ideal diatomic gas (but not the same gas)at 25°C.Which of the following statements about these gases must be true? (There could be more than one correct choice. )

Accepted Answer

The answer of A 10-L flask and a 1-L flask...

Question 17

When water at 0°C freezes,the entropy of the water

Accepted Answer

The entropy of the water decreases when it freezes. This is because the molecules of water become more ordered and arranged in a crystalline structure, which reduces the number of possible arrangements of the water molecules. Therefore, the entropy decreases as the water goes from a disordered liquid to a more ordered solid.

Question 18

An ideal gas is compressed isothermally to one-third of its initial volume.The resulting pressure will be

Accepted Answer

For an ideal gas undergoing an isothermal process, the pressure-volume product (PV) remains constant (Boyle's Law). Therefore, if the volume is reduced to one-third of its initial value, the pressure must increase to three times its initial value to maintain the constant PV product.

Question 19

If the efficiency of a Carnot engine were to be 100%,the heat sink would have to be

Accepted Answer

According to the second law of thermodynamics, it is impossible for a heat engine to completely convert all of the heat it receives into mechanical work. This means that a perfectly efficient engine (which converts all of the input heat into work) cannot exist. The efficiency of a Carnot engine (the most efficient possible heat engine) is given by the ratio of the temperatures of the hot and cold reservoirs, so to increase the efficiency to 100%, the temperature of the cold reservoir must be reduced to absolute zero. Thus, the best choice is A) at absolute zero.

Question 20

An important feature of the Carnot cycle is that

Accepted Answer

The Carnot cycle is the most efficient cycle that can be achieved between two temperatures, and no engine can be more efficient than a Carnot engine operating between the same two temperatures. Its efficiency is determined by the temperature difference between the hot and cold reservoirs, and on the properties of the working substance used. Therefore, choice E is the best choice.

Quiz 18: The Laws of Thermodynamics

When a gas expands adiabatically,

A certain gas is compressed adiabatically.The amount of work done on the gas is 800 J.What is the change in the internal (thermal) energy of the gas?

The process shown on the pV diagram in the figure is an

A certain ideal gas has a molar specific heat at constant volume 7R/2.What is its molar specific heat at constant pressure?

The second law of thermodynamics leads us to conclude that

In a given reversible process,the temperature of an ideal gas is kept constant as the gas is compressed to a smaller volume.Which one of the following statements about the gas is correct?

Which one of the following is a true statement?

Which of the following is a false statement?

A certain ideal gas has a molar specific heat at constant pressure of 33.2 J/mol ∙ K.Its molar specific heat at constant volume is closest to which of the following values? (R = 8.31J/mol ∙ K)

For an ideal gas,

A certain ideal gas has a molar specific heat at constant pressure of 7R/2.What is its molar specific heat at constant volume?

An ideal gas undergoes an isothermal expansion.During this process,its entropy

An ideal gas is compressed isobarically to one-third of its initial volume.The resulting pressure will be

For an ideal gas,

The process shown on the TV graph in the figure is an

A 10-L flask and a 1-L flask each contain two moles of ideal diatomic gas (but not the same gas) at 25°C.Which of the following statements about these gases must be true? (There could be more than one correct choice. )

When water at 0°C freezes,the entropy of the water

An ideal gas is compressed isothermally to one-third of its initial volume.The resulting pressure will be

If the efficiency of a Carnot engine were to be 100%,the heat sink would have to be

An important feature of the Carnot cycle is that