AP Chemistry Flashcards: Absolute Entropy And Entropy Change

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This deck focuses on Absolute Entropy And Entropy Change, giving you a quick way to review the definitions, rules, and examples that matter most for AP Chemistry.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the relationship between entropy and Gibbs free energy for a spontaneous process?

Answer: Entropy increases as Gibbs free energy decreases. Entropy and free energy changes are inversely related.

Flashcard 2: What is the symbol for absolute entropy?

Answer: The symbol for absolute entropy is $S$. Standard notation for entropy, a state function measuring disorder.

Flashcard 3: What is the formula for calculating entropy using microstates?

Answer: $S = k_B \times \ln(W)$. Boltzmann's equation relating entropy to microstates.

Flashcard 4: Find the entropy change for a system where $q_{\text{rev}} = 200 \text{ J}$ and $T = 400 \text{ K}$.

Answer: $\Delta S = 0.5 \text{ J/K}$. Using $\Delta S = \frac{q_{\text{rev}}}{T} = \frac{200}{400}$.

Flashcard 5: State the units for measuring absolute entropy.

Answer: The units for absolute entropy are J/(mol·K). Joules per mole per Kelvin for entropy measurements.

Flashcard 6: What is the entropy change for an irreversible process?

Answer: Entropy change is greater than zero. Irreversible processes always increase total entropy.

Flashcard 7: What is the standard entropy change for a reaction?

Answer: It is the entropy change under standard conditions: 1 atm and 298 K. Standard conditions provide reference state for comparisons.

Flashcard 8: What is the entropy change when a system reaches equilibrium?

Answer: The entropy change is zero at equilibrium. No net change occurs at equilibrium state.

Flashcard 9: What is the relationship between entropy and disorder?

Answer: Entropy is a measure of the disorder or randomness in a system. Higher entropy means greater molecular randomness.

Flashcard 10: What is the significance of $\triangle S_{\text{universe}} > 0$?

Answer: It indicates that the process is spontaneous. Universe entropy increase drives spontaneous processes.

Flashcard 11: What does $k_B$ represent in entropy calculations?

Answer: $k_B$ is the Boltzmann constant. Fundamental constant linking macroscopic and microscopic properties.

Flashcard 12: What is the third law of thermodynamics?

Answer: At absolute zero, the entropy of a perfect crystal is zero. Third law establishes absolute zero entropy reference point.

Flashcard 13: Identify if entropy is a state function.

Answer: Yes, entropy is a state function. Path-independent property depending only on initial and final states.

Flashcard 14: State the entropy change when a solid dissolves in water.

Answer: Entropy typically increases. Dissolution generally increases molecular disorder.

Flashcard 15: What is the standard molar entropy?

Answer: The entropy content of one mole of a substance at standard conditions. Standard reference for entropy comparisons.

Flashcard 16: What does a positive entropy change indicate about a process?

Answer: A positive entropy change indicates increased disorder. System becomes more disordered or random.

Flashcard 17: What is the value of the Boltzmann constant ($k_B$)?

Answer: $k_B = 1.38 \times 10^{-23} \text{ J/K}$. Universal constant in statistical mechanics calculations.

Flashcard 18: What does $q_{\text{rev}}$ represent in entropy calculations?

Answer: $q_{\text{rev}}$ represents the reversible heat exchange. Heat transferred in a reversible process.

Flashcard 19: Identify the sign of entropy change for a spontaneous process.

Answer: The sign of entropy change for a spontaneous process is positive. Positive because universe entropy always increases.

Flashcard 20: Define absolute entropy.

Answer: Absolute entropy is the entropy content of a substance at a given state. Measures total disorder content of a substance.

Flashcard 21: What is the effect of pressure on the entropy of a gas?

Answer: Entropy decreases with increasing pressure. Higher pressure reduces molecular freedom and disorder.

Flashcard 22: Identify the entropy change for a system becoming more ordered.

Answer: The entropy change is negative for increased order. Decreased disorder results in lower entropy.

Flashcard 23: Determine the change in entropy for a system with $q_{\text{rev}} = -100 \text{ J}$ and $T = 300 \text{ K}$.

Answer: $\triangle S = -0.33 \text{ J/K}$. Using $\triangle S = \frac{q_{\text{rev}}}{T} = \frac{-100}{300}$.

Flashcard 24: State the effect of temperature on the absolute entropy of a substance.

Answer: Absolute entropy increases with temperature. Higher temperature increases molecular motion and disorder.

Flashcard 25: Identify the entropy change for a phase transition at constant temperature.

Answer: $\triangle S = \frac{\text{enthalpy of transition}}{T}$. Phase transitions involve latent heat at constant temperature.

Flashcard 26: State the relationship between entropy and the number of microstates.

Answer: Entropy increases with the number of microstates. More microstates mean higher entropy values.

Flashcard 27: State the entropy change for a gas expanding into a vacuum.

Answer: The entropy change is positive. Gas expansion increases molecular disorder significantly.

Flashcard 28: What is the entropy of mixing for ideal gases?

Answer: Entropy of mixing is positive for ideal gases. Mixing increases total system disorder.

Flashcard 29: Which law of thermodynamics relates to entropy?

Answer: The second law of thermodynamics relates to entropy. Second law states universe entropy always increases.

Flashcard 30: What is the formula for entropy change ($\triangle S$)?

Answer: $\triangle S = S_{\text{final}} - S_{\text{initial}}$. Final state entropy minus initial state entropy.