AP Chemistry Flashcards: Concentration Changes Over Time

What this deck covers

This deck focuses on Concentration Changes Over Time, 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: Which factor does NOT affect the rate constant $k$?

Answer: Concentration of reactants. Rate constant depends only on temperature and catalyst.

Flashcard 2: State the Arrhenius equation.

Answer: $k = A e^{-\frac{E_a}{RT}}$. Exponential relationship between rate constant and temperature.

Flashcard 3: How does temperature affect reaction rate?

Answer: Higher temperature increases reaction rate. More molecular collisions occur at higher temperatures.

Flashcard 4: How is the rate constant $k$ affected by temperature increase?

Answer: The rate constant $k$ increases. Higher temperature provides more kinetic energy for reactions.

Flashcard 5: Identify the units of the rate constant $k$ for a first-order reaction.

Answer: Units: $\text{s}^{-1}$. First-order rate constant has units of reciprocal time.

Flashcard 6: Identify the units of the rate constant $k$ for a zero-order reaction.

Answer: Units: $\text{M} \text{s}^{-1}$. Zero-order reactions have rate units of concentration per time.

Flashcard 7: Identify the units of the rate constant $k$ for a second-order reaction.

Answer: Units: $\text{M}^{-1} \text{s}^{-1}$. Second-order rate constant has units of reciprocal concentration-time.

Flashcard 8: Determine the reaction order: $[\text{A}]$ halves every 20 seconds regardless of initial concentration.

Answer: First-order reaction. Constant half-life indicates first-order kinetics.

Flashcard 9: Determine the reaction order: Rate is independent of $[\text{A}]$ concentration.

Answer: Zero-order reaction. Rate independent of concentration changes.

Flashcard 10: Calculate the half-life if $k = 0.693 \text{s}^{-1}$ for a first-order reaction.

Answer: $t_{1/2} = 1 \text{s}$. Using $t_{1/2} = \frac{\ln(2)}{k}$ formula.

Flashcard 11: What is the relationship between reaction rate and concentration for a first-order reaction?

Answer: Rate is directly proportional to concentration. Rate equals rate constant times concentration.

Flashcard 12: Determine the reaction order: Doubling $[\text{A}]$ quadruples the reaction rate.

Answer: Second-order reaction. Rate proportional to concentration squared.

Flashcard 13: How do you determine the reaction order from a concentration vs. time graph?

Answer: Analyze the shape of the plot. Different orders produce characteristic curve shapes.

Flashcard 14: Calculate the rate if $k = 0.5 \text{s}^{-1}$ and $[\text{A}] = 2 \text{M}$ for a first-order reaction.

Answer: Rate = $1 \text{M} \text{s}^{-1}$. Rate equals $k$ times concentration for first-order.

Flashcard 15: What is the half-life formula for a second-order reaction?

Answer: $t_{1/2} = \frac{1}{k[\text{A}]_0}$. Half-life inversely proportional to initial concentration.

Flashcard 16: What is the effect of a catalyst on the overall reaction rate?

Answer: Increases overall reaction rate. Provides faster pathway without changing equilibrium.

Flashcard 17: What does the slope of a second-order reaction plot $\frac{1}{[\text{A}]}$ vs. time represent?

Answer: Rate constant $k$. Slope of reciprocal concentration vs time plot.

Flashcard 18: What is the role of the frequency factor $A$ in the Arrhenius equation?

Answer: Represents collision frequency factor. Pre-exponential factor in Arrhenius equation.

Flashcard 19: Identify the graph shape for a zero-order reaction concentration vs. time plot.

Answer: Straight line downward. Constant rate produces linear concentration decrease.

Flashcard 20: What is the effect of a catalyst on activation energy $E_a$?

Answer: Decreases activation energy $E_a$. Provides alternative pathway with lower energy barrier.

Flashcard 21: State the integrated rate law for a zero-order reaction.

Answer: $[\text{A}]_t = [\text{A}]_0 - kt$. Linear decrease with time for zero-order kinetics.

Flashcard 22: How does the concentration of reactants change over time in a first-order reaction?

Answer: Decreases exponentially. Rate proportional to remaining concentration.

Flashcard 23: Which order of reaction has a constant half-life regardless of initial concentration?

Answer: First-order reaction. Constant half-life is characteristic of first-order kinetics.

Flashcard 24: How does the concentration of reactants change over time in a second-order reaction?

Answer: Decreases more steeply than first-order. Rate proportional to concentration squared.

Flashcard 25: What is the half-life formula for a zero-order reaction?

Answer: $t_{1/2} = \frac{[\text{A}]_0}{2k}$. Half-life depends on initial concentration for zero-order.

Flashcard 26: What is the rate law expression for a reaction $aA + bB \rightarrow cC$?

Answer: $\text{rate} = k[A]^m[B]^n$. Rate depends on concentrations raised to their respective orders.

Flashcard 27: Identify the graph shape for a first-order reaction concentration vs. time plot.

Answer: Exponential decay curve. Rate proportional to concentration creates exponential decay.

Flashcard 28: Identify the graph shape for a second-order reaction concentration vs. time plot.

Answer: Inversely proportional curve. Rate proportional to concentration squared.

Flashcard 29: State the integrated rate law for a zero-order reaction.

Answer: $[\text{A}]_t = [\text{A}]_0 - kt$. Linear decrease with time for zero-order kinetics.

Flashcard 30: Which order of reaction has a constant half-life regardless of initial concentration?

Answer: First-order reaction. Constant half-life is characteristic of first-order kinetics.