AP Chemistry Flashcards: Energy Diagrams

What this deck covers

This deck focuses on Energy Diagrams, 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: How are endothermic reactions graphically depicted?

Answer: Products higher than reactants on energy diagram. Starting point below ending point on diagram.

Flashcard 2: Find the activation energy in a given energy diagram.

Answer: Identify the energy difference from reactants to peak. Measure vertical distance from start to peak.

Flashcard 3: What does the height of the activation energy barrier indicate?

Answer: The difficulty of initiating the reaction. Higher barrier means slower reaction rate.

Flashcard 4: How is the overall energy change ($\triangle H$) shown on an energy diagram?

Answer: Difference in energy between reactants and products. Vertical distance between reactant and product levels.

Flashcard 5: What is the significance of the transition state in a reaction?

Answer: It is the highest energy state, representing a critical point. Unstable state where bond breaking and forming occur.

Flashcard 6: How is activation energy represented on an energy diagram?

Answer: The difference in energy from reactants to transition state. Vertical distance from reactants to the peak.

Flashcard 7: Describe how an energy diagram would change with a catalyst.

Answer: Lower peaks, but reactants and products remain unchanged. Same $\triangle H$ but alternative lower-energy pathway.

Flashcard 8: What does a lower peak in a catalyzed reaction's energy diagram indicate?

Answer: Lower activation energy. Easier pathway increases reaction rate.

Flashcard 9: Identify the energy difference indicating the rate-determining step in multi-step reactions.

Answer: The highest energy barrier between intermediates. The step with highest activation energy controls rate.

Flashcard 10: What indicates a multi-step reaction on an energy diagram?

Answer: Multiple peaks and valleys. Each peak represents a separate elementary step.

Flashcard 11: Identify the x-axis label in an energy diagram.

Answer: Reaction coordinate. Shows the progress of the reaction from start to finish.

Flashcard 12: Identify the y-axis label in an energy diagram.

Answer: Potential energy. Represents the energy content of species during reaction.

Flashcard 13: State the meaning of activation energy.

Answer: The energy required to initiate a reaction. Minimum energy needed for reactants to form products.

Flashcard 14: Identify the reaction type if the products are lower in energy than the reactants.

Answer: Exothermic. Energy flows out when products form at lower energy.

Flashcard 15: What is the effect of temperature on an energy diagram?

Answer: Temperature does not change the diagram shape but can affect rates. Affects kinetics but not thermodynamic energy levels.

Flashcard 16: How do intermediates appear on an energy diagram?

Answer: As valleys between peaks. Local minima between transition state peaks.

Flashcard 17: Identify the effect of a higher transition state energy on reaction rate.

Answer: Slower reaction rate due to higher activation energy. Higher energy barrier reduces reaction rate significantly.

Flashcard 18: Identify the sign of $\triangle H$ for an endothermic reaction.

Answer: Positive. Products are higher in energy than reactants.

Flashcard 19: When are intermediates formed in a reaction?

Answer: In multi-step reactions, between transition states. Formed at energy minima between reaction steps.

Flashcard 20: Determine the $\triangle H$ from an energy diagram with values labeled.

Answer: Subtract reactant energy from product energy. Calculate final minus initial energy levels.

Flashcard 21: Identify a characteristic of a reversible reaction in an energy diagram.

Answer: Both forward and reverse activation energies are shown. Can proceed in either direction with different barriers.

Flashcard 22: State the effect of pressure on an energy diagram.

Answer: Pressure does not alter energy diagram shape. Energy levels remain constant regardless of pressure.

Flashcard 23: How are reversible reactions depicted in an energy diagram?

Answer: Two activation energies: one for forward, one for reverse. Different energy barriers for each reaction direction.

Flashcard 24: Identify the sign of $\triangle H$ for an exothermic reaction.

Answer: Negative. Products are lower in energy than reactants.

Flashcard 25: What does a valley in an energy diagram represent?

Answer: Intermediate. A stable species formed temporarily during the reaction.

Flashcard 26: What does a flat section on an energy diagram suggest?

Answer: A stable intermediate or plateau in energy change. Shows constant energy region or stable intermediate.

Flashcard 27: What is the difference between exothermic and endothermic reactions in energy diagrams?

Answer: Exothermic: products lower; Endothermic: products higher. Based on final energy relative to starting energy.

Flashcard 28: Identify the reaction type if the products are higher in energy than the reactants.

Answer: Endothermic. Energy must be added when products are higher energy.

Flashcard 29: What does the area under the curve in an energy diagram represent?

Answer: It is not directly meaningful; focus on energy differences. Curve area doesn't represent meaningful energy quantity.

Flashcard 30: What does the width of the transition state in an energy diagram represent?

Answer: No specific width significance; focus on height. Width is not meaningful; only peak height matters.