5.6 Multistep Reaction Energy Profile

• A single-step reaction occurs in multiple stages.

  False
• Multistep reactions are simpler to analyze than single-step reactions.

  False
• Products exist before any reaction steps begin.

  False
• What are products in a multistep reaction?

  Final substances formed
• What happens to products in a multistep reaction after all steps are completed?

  Final substances remain
• Intermediate substances may be formed and consumed in a multistep reaction.

  True
• Intermediate substances are only formed in single-step reactions.

  False
• What is the high-energy species formed at the transition state called?

  Activated complex
• What is the formula for calculating the overall enthalpy change in a multistep reaction?

  $\Delta H_{\text{overall}} =$$\Delta H_{\text{step 1}} +$$\Delta H_{\text{step 2}} +$$\ldots +$$\Delta H_{\text{step n}}$
• A multistep reaction is a chemical reaction that occurs in multiple steps
• Multistep reactions involve intermediate steps and products
• What are reactants in a multistep reaction?

  Substances at the start
• Match the type of reaction with its characteristic:

  Single-Step Reaction ↔️ Occurs in one step

  Multistep Reaction ↔️ Occurs in multiple steps

  Reactants ↔️ Substances at the start

  Products ↔️ Substances formed at the end
• Products are identified as the final substances formed at the end
• What are the substances present at the start of a reaction called?

  Reactants
• In a multistep reaction, what are the initial substances called?

  Reactants
• What do transition states and activated complexes represent in a reaction pathway?

  Highest energy point
• Transition states and activated complexes are stable species.

  False
• What is a multistep reaction?

  Multiple steps or stages
• How many activation energy barriers are present in the energy profile of a multistep reaction?

  Multiple
• Reactants are consumed or transformed during the reaction
• Multistep reactions have multiple activation energy barriers in their energy profile.

  True
• Reactants in a multistep reaction are the initial substances present.

  True
• The final substances formed in a reaction are called products
• The final substances formed in a multistep reaction are called products
• A transition state is a specific atomic configuration at the peak of the energy barrier
• The overall enthalpy change in a multistep reaction is the sum of the enthalpy changes for each individual step
• What does analyzing the overall enthalpy change in a multistep reaction provide insights into?

  Energetics and feasibility
• Analyzing the energy profile of a multistep reaction helps understand its mechanism and kinetics.

  True
• In the example reaction 2NO₂ → N₂O₄, the product in a single-step reaction is N₂O₄
• Steps in a two-step multistep reaction for the conversion of 2NO₂ to N₂O₄

  1️⃣ 2NO₂ → 2NO + O₂

  2️⃣ 2NO + O₂ → N₂O₄
• A transition state is an atomic configuration at the peak of the energy barrier where bonds are fully formed and broken.

  False
• Steps to calculate the overall enthalpy change (ΔH) in a multistep reaction

  1️⃣ Determine ΔH for each individual step

  2️⃣ Sum the ΔH values for all steps
• The rate-determining step in a multistep reaction limits the overall reaction rate.

  True
• The step with the highest activation energy in a multistep reaction is the fastest step.

  False
• A single-step reaction involves intermediate steps and products.

  False
• What is a transition state in chemical kinetics?

  High-energy peak state
• The overall enthalpy change in a multistep reaction is the sum of the enthalpy changes for each step.


  True
• In the reaction 2NO₂ → N₂O₄, if step 1 is slower, it is the rate-determining step.
• A multistep reaction energy profile has multiple activation energy barriers