AP Chemistry Flashcards: Introduction To Entropy

What this deck covers

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

How to use these flashcards

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: Calculate the entropy change: $q = 200 \text{ J}$, $T = 400 \text{ K}$.

Answer: $\Delta S = 0.5 \text{ J/K}$. Apply $\Delta S = q/T = 200/400$ formula.

Flashcard 2: Identify the equation relating entropy change to heat and temperature.

Answer: $\Delta S = \frac{q_{\text{rev}}}{T}$. Relates entropy change to reversible heat transfer at constant temperature.

Flashcard 3: Does entropy increase or decrease in a system where volume increases?

Answer: Entropy increases when volume increases. Larger volume provides more molecular position options.

Flashcard 4: What is the entropy change when a system becomes more ordered?

Answer: The entropy change is negative. Increased order corresponds to decreased entropy.

Flashcard 5: Identify the entropy change sign for a reaction producing more moles of gas.

Answer: The entropy change is positive. More gas molecules create greater molecular disorder.

Flashcard 6: How does entropy change with temperature in an isolated system?

Answer: Entropy increases with temperature. Higher temperature increases molecular kinetic energy and disorder.

Flashcard 7: What is the value of Boltzmann's constant $k_B$?

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

Flashcard 8: Identify the process: $\Delta S > 0$ and $\Delta G < 0$ at constant $T$ and $P$.

Answer: The process is spontaneous. Positive entropy change indicates thermodynamic favorability.

Flashcard 9: What is the entropy trend when a substance changes from gas to liquid?

Answer: Entropy decreases. Gas-to-liquid transition reduces molecular freedom.

Flashcard 10: Which process increases entropy: freezing or melting?

Answer: Melting increases entropy. Melting increases molecular disorder compared to freezing.

Flashcard 11: Which has higher entropy: a mixture of gases or pure gases separately?

Answer: A mixture of gases has higher entropy. Mixing increases possible molecular arrangements.

Flashcard 12: Which has higher entropy: $1 \text{ mol}$ of $H_2O$ gas or $1 \text{ mol}$ of $H_2O$ liquid?

Answer: $1 \text{ mol}$ of $H_2O$ gas has higher entropy. Gas phase provides maximum molecular freedom.

Flashcard 13: Which entropy change is greater: solid to liquid or liquid to gas?

Answer: Liquid to gas has a greater entropy change. Gas phase transition involves much greater volume expansion.

Flashcard 14: Calculate the entropy change: $q = 200 \text{ J}$, $T = 400 \text{ K}$.

Answer: $\Delta S = 0.5 \text{ J/K}$. Apply $\Delta S = q/T = 200/400$ formula.

Flashcard 15: Which has a greater entropy: a solid or its corresponding liquid?

Answer: The corresponding liquid has greater entropy. Liquid molecules have greater freedom than solid.

Flashcard 16: Does entropy increase or decrease during the dissolution of salt in water?

Answer: Entropy increases during dissolution. Dissolution disperses ions, increasing system disorder.

Flashcard 17: What is the term for entropy related to the number of possible microstates?

Answer: Statistical entropy. Statistical mechanics approach to entropy measurement.

Flashcard 18: Which process decreases entropy: condensation or vaporization?

Answer: Condensation decreases entropy. Condensation creates order by reducing molecular freedom.

Flashcard 19: Choose the process with a positive entropy change: dissolution or crystallization.

Answer: Dissolution has a positive entropy change. Dissolution disperses solute particles, increasing disorder.

Flashcard 20: What is the entropy change for a system in thermal equilibrium?

Answer: The entropy change is zero. Equilibrium means no net entropy change occurs.

Flashcard 21: Find $\Delta S$ for $q = 300 \text{ J}$ at $T = 400 \text{ K}$.

Answer: $\Delta S = 0.75 \text{ J/K}$. Direct calculation using $\Delta S = q/T$.

Flashcard 22: What is the relationship between entropy and microstates?

Answer: $S = k_B \ln \Omega$. Boltzmann's equation linking macroscopic entropy to microscopic states.

Flashcard 23: What is the standard entropy change formula for a reaction?

Answer: $\Delta S = S_\text{products} - S_\text{reactants}$. Standard formula for calculating entropy change in chemical reactions.

Flashcard 24: Which has higher entropy: $1 \text{ mol}$ of $O_2$ gas or $1 \text{ mol}$ of $O_2$ liquid?

Answer: $1 \text{ mol}$ of $O_2$ gas has higher entropy. Gas phase has much greater molecular freedom.

Flashcard 25: Calculate $\Delta S$ given $q = 500 \text{ J}$ and $T = 250 \text{ K}$.

Answer: $\Delta S = 2 \text{ J/K}$. Standard entropy calculation using given values.

Flashcard 26: Does entropy increase or decrease when ice melts?

Answer: Entropy increases when ice melts. Phase transition from ordered solid to liquid state.

Flashcard 27: What happens to entropy when a gas expands into a vacuum?

Answer: Entropy increases when a gas expands into a vacuum. Free expansion increases molecular spatial distribution.

Flashcard 28: Identify the entropy change when a perfect crystal is at absolute zero.

Answer: Entropy is zero at absolute zero for a perfect crystal. Third law establishes absolute entropy reference point.

Flashcard 29: What is the sign of entropy change for an exothermic process with gas decrease?

Answer: The entropy change is negative. Gas decrease reduces disorder despite heat release.

Flashcard 30: Determine $\Delta S$ for a reversible isothermal expansion with $q = 150 \text{ J}$, $T = 300 \text{ K}$.

Answer: $\Delta S = 0.5 \text{ J/K}$. Apply entropy formula for isothermal reversible process.