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: 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 2: What is the effect of a catalyst on the rate of reaction?

Answer: Increases the reaction rate. Lowers activation energy without being consumed.

Flashcard 3: 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 4: 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 5: What is the half-life formula for a first-order reaction?

Answer: $t_{1/2} = \frac{\ln(2)}{k}$. Constant half-life independent of initial concentration.

Flashcard 6: Determine the reaction order: Rate is independent of $[\text{A}]$ concentration.

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

Flashcard 7: Which factor does NOT affect the rate constant $k$?

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

Flashcard 8: 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 9: 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 10: State the integrated rate law for a first-order reaction.

Answer: $[\text{A}]_t = [\text{A}]_0 e^{-kt}$. Exponential decay relationship for first-order kinetics.

Flashcard 11: 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 12: 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 13: Determine the reaction order: Rate is independent of $[\text{A}]$ concentration.

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

Flashcard 14: 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 15: 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 16: 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 17: State the Arrhenius equation.

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

Flashcard 18: Identify the graph shape for a second-order reaction concentration vs. time plot.

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

Flashcard 19: 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 20: 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 21: What is the effect of concentration on the rate for a zero-order reaction?

Answer: Rate is independent of concentration. Rate remains constant regardless of concentration.

Flashcard 22: Which factor does NOT affect the rate constant $k$?

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

Flashcard 23: 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 24: How does the concentration of reactants change over time in a first-order reaction?

Answer: Decreases exponentially. Rate proportional to remaining concentration.

Flashcard 25: 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 26: 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 27: What is the effect of a catalyst on the overall reaction rate?

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

Flashcard 28: 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 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: What is the effect of a catalyst on the overall reaction rate?

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

Flashcard 31: 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 32: Determine the reaction order: Doubling $[\text{A}]$ quadruples the reaction rate.

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

Flashcard 33: 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 34: 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 35: 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 36: Determine the reaction order: Doubling $[\text{A}]$ quadruples the reaction rate.

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

Flashcard 37: 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 38: 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 39: 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 40: How does temperature affect reaction rate?

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

Flashcard 41: How does the concentration of reactants change over time in a first-order reaction?

Answer: Decreases exponentially. Rate proportional to remaining concentration.

Flashcard 42: 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 43: 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 44: 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 45: 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 46: 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 47: State the integrated rate law for a second-order reaction.

Answer: $\frac{1}{[\text{A}]_t} = \frac{1}{[\text{A}]_0} + kt$. Reciprocal concentration increases linearly with time.

Flashcard 48: 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 49: How does temperature affect reaction rate?

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

Flashcard 50: Identify the graph shape for a zero-order reaction concentration vs. time plot.

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

Flashcard 51: 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 52: 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 53: What is the Arrhenius equation used for?

Answer: Calculating the temperature dependence of the rate constant. Relates rate constant to temperature and activation energy.

Flashcard 54: 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 55: 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 56: 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 57: What does the slope of a first-order reaction plot $[\text{ln[A]}]$ vs. time represent?

Answer: Negative rate constant $-k$. Slope of $\ln[A]$ vs time plot.

Flashcard 58: 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 59: 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 60: Identify the graph shape for a zero-order reaction concentration vs. time plot.

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

Flashcard 61: 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 62: State the Arrhenius equation.

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

Flashcard 63: 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 64: 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 65: How does the concentration of reactants change over time in a first-order reaction?

Answer: Decreases exponentially. Rate proportional to remaining concentration.

Flashcard 66: What happens to the concentration of reactants over time in a zero-order reaction?

Answer: Decreases linearly over time. Constant rate independent of remaining concentration.