AP Chemistry Flashcards: Introduction To Reaction Mechanisms

What this deck covers

This deck focuses on Introduction To Reaction Mechanisms, 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 does the term 'reaction order' refer to?

Answer: The sum of the exponents in the rate law expression. Determines how concentration changes affect overall rate.

Flashcard 2: What is the role of activation energy in a reaction mechanism?

Answer: The minimum energy required to initiate a chemical reaction. Energy barrier that must be overcome for reaction to occur.

Flashcard 3: What is the steady-state approximation?

Answer: An assumption that the concentration of intermediates remains constant. Rate of formation equals rate of consumption for intermediates.

Flashcard 4: What does the symbol $k$ represent in kinetics?

Answer: The rate constant of a reaction. Proportionality constant in rate law expressions.

Flashcard 5: How does molecular orientation affect reaction rate?

Answer: Proper orientation during collisions is necessary for reaction. Molecules must collide with correct geometry for reaction.

Flashcard 6: What does the symbol $Ea$ represent in the Arrhenius equation?

Answer: Activation energy. Energy barrier parameter in temperature-dependent rate equation.

Flashcard 7: What is the role of collision frequency in reaction rate?

Answer: Higher collision frequency can increase the reaction rate. More collisions per unit time increases reaction probability.

Flashcard 8: What is the half-life ($t_{1/2}$) of a first-order reaction?

Answer: $t_{1/2} = \frac{0.693}{k}$. Time required for concentration to decrease by half.

Flashcard 9: What does 'R' represent in the Arrhenius equation?

Answer: The universal gas constant. Fundamental constant linking energy and temperature scales.

Flashcard 10: What does the term 'rate law' refer to?

Answer: An equation that relates the rate of reaction to the concentration of reactants. Mathematical expression relating reaction rate to concentrations.

Flashcard 11: What is the purpose of using the steady-state approximation?

Answer: To simplify the analysis of complex reaction mechanisms. Eliminates need to track rapidly changing intermediate concentrations.

Flashcard 12: What is the Lindemann mechanism?

Answer: A mechanism describing unimolecular reactions through a two-step process. Explains pressure dependence of unimolecular reaction rates.

Flashcard 13: What is the effect of temperature on the rate constant $k$?

Answer: Typically, $k$ increases with increasing temperature. Exponential relationship described by Arrhenius equation.

Flashcard 14: What does a reaction mechanism describe?

Answer: The detailed steps of how a reaction proceeds from reactants to products. Shows elementary steps connecting reactants to products.

Flashcard 15: What is the effect of concentration on reaction rate?

Answer: Increased concentration generally increases reaction rate. More reactant molecules lead to more frequent collisions.

Flashcard 16: What is the significance of the rate-determining step?

Answer: It limits the overall reaction rate. Slowest step controls overall reaction speed like bottleneck.

Flashcard 17: What characterizes a bimolecular reaction?

Answer: A reaction involving two reacting species. Has molecularity of two, most common elementary reaction type.

Flashcard 18: What is the difference between a catalyst and an intermediate?

Answer: Catalysts are not consumed; intermediates are formed and consumed. Both help reaction proceed but have different consumption patterns.

Flashcard 19: Define termolecular reaction.

Answer: An elementary reaction involving three molecules. Very rare due to low probability of three molecules colliding simultaneously.

Flashcard 20: State the formula for the Arrhenius equation.

Answer: $k = Ae^{-Ea/RT}$. Shows exponential dependence of rate constant on temperature.

Flashcard 21: Identify the units of a rate constant for a second-order reaction.

Answer: $M^{-1}s^{-1}$. Units account for concentration dependence in second-order kinetics.

Flashcard 22: What is the typical unit for the universal gas constant ($R$)?

Answer: $8.314 J mol^{-1} K^{-1}$. Standard SI units for gas constant in energy calculations.

Flashcard 23: What is a unimolecular reaction?

Answer: A reaction involving a single molecule undergoing change. Has molecularity of one and follows first-order kinetics.

Flashcard 24: Define 'reaction profile'.

Answer: A graph showing the energy changes during a reaction. Visualizes energy barriers and intermediates along reaction pathway.

Flashcard 25: How does temperature affect reaction rate according to the Arrhenius equation?

Answer: Increasing temperature increases the reaction rate. Higher temperature increases molecular energy and collision frequency.

Flashcard 26: Identify the role of a catalyst in a reaction mechanism.

Answer: A substance that increases reaction rate without being consumed. Lowers activation energy by providing alternative pathway.

Flashcard 27: What is the effect of a catalyst on activation energy?

Answer: A catalyst lowers the activation energy of a reaction. Provides alternative pathway requiring less energy input.

Flashcard 28: Identify the units of a rate constant for a zero-order reaction.

Answer: $M s^{-1}$. Units reflect constant rate independent of concentration.

Flashcard 29: What is the rate-determining step?

Answer: The slowest step in a reaction mechanism that determines the overall rate. Acts as bottleneck controlling overall reaction speed.

Flashcard 30: Identify the transition state of a reaction.

Answer: A high-energy, unstable arrangement of atoms at the peak of a reaction coordinate. Maximum energy point along reaction coordinate diagram.