Statistical Thermodynamics Concepts

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Questions and Answers

In the context of gas spreading between two flasks, what best describes the state of the gas molecules after the stopcock is opened?

The gas molecules are equally distributed, resulting in a state of perfect order.
The arrangement of gas molecules becomes less random and more ordered.
The gas molecules remain confined to the original flask, maintaining their initial order.
The arrangement of gas molecules is more random or disordered compared to when confined. (correct)

What is the primary goal of statistical thermodynamics?

To develop new mathematical tools for describing thermodynamic properties.
To analyze the behavior of individual molecules without considering the bulk properties of matter.
To connect the microscopic and macroscopic descriptions of matter using statistics and probability. (correct)
To describe the properties of macroscopic matter without considering microscopic structure.

How does the number of possible arrangements of gas molecules in a system relate to the expansion of the gas?

The number of possible arrangements does not affect gas expansion.
A smaller number of possible arrangements leads to gas expansion.
A larger number of possible arrangements helps explain why the gas expands. (correct)
The number of possible arrangements determines the rate of gas compression.

When considering one mole of an ideal gas in a defined thermodynamic state, what microscopic property is directly relevant to determining the entropy of the gas?

The positions and speeds of all the molecules at a given instant. (A) Signup and view all the answers

Which of the following best describes the traditional approach of thermodynamics before the development of statistical thermodynamics?

Describing macroscopic properties of matter without considering microscopic structure. (C) Signup and view all the answers

What does specifying the temperature and volume of an ideal gas allow one to define?

A particular thermodynamic state of the gas. (A) Signup and view all the answers

How did the development of statistical thermodynamics change the study of thermodynamics?

It allowed for the connection of microscopic behavior to macroscopic properties. (B) Signup and view all the answers

For a certain process, the entropy change of the system is -50 J/K and the entropy change of the surroundings is +50 J/K. According to the second law of thermodynamics, what can be concluded about this process?

The process is reversible. (B) Signup and view all the answers

Which of the following statements best describes the second law of thermodynamics?

The entropy of the universe tends to increase in spontaneous processes. (C) Signup and view all the answers

What is the significance of a 'snapshot' of the positions and speeds of all molecules in a gas at a given instant?

It provides insight into the microstates that contribute to the gas's entropy. (A) Signup and view all the answers

A chemical reaction occurs in a closed system. If the entropy of the system decreases, what must be true about the entropy change of the surroundings for the process to be spontaneous?

The entropy of the surroundings must increase by more than the system decreases. (C) Signup and view all the answers

For a reversible process, which equation accurately describes the relationship between the entropy change of the system ($\Delta S_{sys}$), the entropy change of the surroundings ($\Delta S_{surr}$), and the entropy change of the universe ($\Delta S_{univ}$)?

$\Delta S_{univ} = \Delta S_{sys} + \Delta S_{surr} = 0$ (D) Signup and view all the answers

Consider a process where heat is added to a system at constant temperature. Under what conditions would this process be considered reversible?

If the heat transfer occurs infinitesimally slowly. (C) Signup and view all the answers

A gas expands into a vacuum. What can be said about the entropy change of the surroundings for this process?

The entropy of the surroundings does not change. (B) Signup and view all the answers

The melting of ice at 1°C is considered an irreversible process. What would need to happen to make this process reversible?

Melt the ice at a temperature infinitesimally above 0°C. (D) Signup and view all the answers

What is the significance of the second law of thermodynamics in determining the spontaneity of a process?

It provides a criterion based on the entropy change of the universe. (D) Signup and view all the answers

How does an increase in temperature affect the molecular speeds within an ideal gas?

It increases the average molecular speed and broadens the distribution of speeds. (B) Signup and view all the answers

Which of the following statements accurately contrasts the translational motion of molecules in different states of matter?

Molecules in gases have the most freedom of translational motion, followed by liquids, then solids. (D) Signup and view all the answers

Which type of motion is unique to molecules, compared to individual atoms?

Vibrational and rotational motion (B) Signup and view all the answers

What best describes 'motional energy'?

The collective energy from translational, vibrational, and rotational movements of a molecule. (A) Signup and view all the answers

How does the capacity for vibrational and rotational motion affect the number of possible microstates in a system of real molecules compared to an ideal gas?

Real molecules have a greater number of microstates because these motions add complexity. (A) Signup and view all the answers

Consider two gases, one composed of monatomic ideal gas particles and the other of diatomic molecules. If both gases are at the same temperature, which statement is correct regarding their average translational kinetic energy?

Both gases will have the same average translational kinetic energy because temperature is the same for both. (A) Signup and view all the answers

A sealed container contains both helium (He) atoms and carbon dioxide ($CO_2$) molecules at the same temperature. Which of the following statements is most accurate?

The He atoms and $CO_2$ molecules have the same average translational kinetic energy, but the $CO_2$ molecules have additional motional energy due to vibration and rotation. (B) Signup and view all the answers

Imagine a system where the temperature of a gas is increased. What is the most likely outcome regarding the energy distribution among the molecules?

The average kinetic energy increases, and the distribution of molecular speeds broadens, with more molecules at higher speeds. (D) Signup and view all the answers

Which scenario would generally lead to an increase in the entropy of a system?

The formation of gases from liquids. (A) Signup and view all the answers

Consider a reaction where a complex molecule breaks down into several smaller molecules in the gaseous phase. What is the most likely outcome regarding entropy?

The entropy will likely increase, as there are more gas molecules and thus greater disorder. (A) Signup and view all the answers

When silver ions ($Ag^+$) and chloride ions ($Cl^$) in solution combine to form solid silver chloride ($AgCl$), what happens to the entropy of the system?

The entropy decreases because the ions are more ordered in the solid. (C) Signup and view all the answers

In the reaction $4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$, how does the entropy change, and why?

Decreases, because a gas is being consumed to form a solid. (D) Signup and view all the answers

Consider the reaction $N_2(g) + O_2(g) \rightarrow 2NO(g)$. What can be predicted about the change in entropy ($\Delta S$) for this reaction?

$\Delta S$ will be close to zero because the number of moles of gas remains the same. (A) Signup and view all the answers

Gases are compressed to a smaller volume at a constant temperature. How does this affect entropy?

Entropy decreases as molecules are more confined. (D) Signup and view all the answers

A solute dissolves in a solvent. What would lead to the greatest increase in entropy?

A large, complex molecule dissolving into smaller fragments. (D) Signup and view all the answers

Consider a system where ice melts into liquid water at $0 \degree C$. What statement accurately describes the entropy change?

Entropy increases because the water molecules gain more freedom of movement. (A) Signup and view all the answers

What is the primary reason that entropy generally increases with an increasing number of atoms in a molecule?

Larger molecules have more possible microstates, leading to increased disorder. (D) Signup and view all the answers

Consider the reaction: $A(g) + B(g) \rightarrow 2C(g)$. If the standard molar entropies ($S^\circ$) are: $A(g) = 150 \frac{J}{mol \cdot K}$, $B(g) = 200 \frac{J}{mol \cdot K}$, and $C(g) = 180 \frac{J}{mol \cdot K}$, what is the standard entropy change ($\Delta S^\circ$) for this reaction?

$10 \frac{J}{K}$ (D) Signup and view all the answers

In the reaction $N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$, the standard entropy change ($\Delta S^\circ$) is negative. Which statement provides the best explanation for this observation?

The number of gas molecules decreases from reactants to products, leading to a decrease in disorder. (D) Signup and view all the answers

Which of the following processes would you expect to have the largest positive change in entropy?

Sublimation of dry ice (B) Signup and view all the answers

If a reaction involves an increase in the number of gaseous molecules and a significant increase in temperature, what can be predicted about the change in entropy ($\Delta S$) for the reaction?

$\Delta S$ will likely be positive because both the increase in gas molecules and temperature contribute to increased disorder. (B) Signup and view all the answers

Consider two gases, A and B, at the same temperature. Gas A has a higher standard molar entropy than Gas B. What can be inferred about the complexity or structure of Gas A compared to Gas B?

Gas A must be composed of more complex or larger molecules than Gas B. (A) Signup and view all the answers

For the reaction $2CO(g) + O_2(g) \rightarrow 2CO_2(g)$, predict the sign of $\Delta S^\circ$ (standard entropy change).

$\Delta S^\circ < 0$ (negative) (C) Signup and view all the answers

Which factor would LEAST likely influence the entropy change ($ \Delta S $) in a chemical reaction?

The color of the reactants and products. (B) Signup and view all the answers

In the context of thermodynamics, which scenario best exemplifies an irreversible process?

Heat flowing spontaneously from a hot cup of coffee to a cooler room. (D) Signup and view all the answers

What condition is necessary for heat transfer between a system and its surroundings to be considered reversible?

The temperature difference between the system and surroundings must be infinitesimally small. (D) Signup and view all the answers

Consider water in a closed container that is first evaporated and then condensed. Under what conditions would this two-step process most closely approximate a reversible process?

If the temperature and pressure are precisely controlled to maintain equilibrium during both phases. (A) Signup and view all the answers

In the context of an ideal gas expanding isothermally, what factor primarily determines whether the expansion is reversible or irreversible?

The presence or absence of friction during the expansion. (B) Signup and view all the answers

Which of the following best describes a reversible process?

A process that can be reversed by an infinitesimal change in a property. (D) Signup and view all the answers

A system undergoes a process where its temperature is maintained at $T + dT$, where $dT$ represents an infinitesimally small temperature difference compared to its surroundings at temperature $T$. What is the immediate consequence of this condition regarding heat flow?

Heat flows from the system to the surroundings. (C) Signup and view all the answers

Which process is least likely to be considered reversible in a real-world scenario?

The rapid combustion of fuel in an engine. (B) Signup and view all the answers

In a cylinder-piston arrangement, an ideal gas expands against the piston. Which factor would cause this process to deviate most significantly from being considered reversible?

Increasing the speed at which the piston moves during expansion. (A) Signup and view all the answers

Flashcards

Water Phase Change Reversibility

A process where water evaporates and then condenses back. It's not necessarily reversible due to factors like energy dissipation.

Spontaneous Heat Flow

Heat flow naturally goes from hot to cold, not the other way around.