5.2 Reaction profiles

• A reaction profile is a graph that shows how the energy of reactants and products changes during a chemical reaction
• What happens to energy during an exothermic reaction?

  Energy is released
• Match the feature of a reaction profile with its description:

  Reactants ↔️ Starting energy level

  Products ↔️ Final energy level

  Activation energy ↔️ Minimum energy to start reaction

  Enthalpy change ↔️ Overall energy change
• Match the reaction type with its energy level change:

  Exothermic ↔️ Products have lower energy

  Endothermic ↔️ Products have higher energy
• The transition state is a high-energy, unstable intermediate
• A reaction profile shows the energy changes during a chemical reaction.


  True
• What is the energy change in an endothermic reaction?

  Energy is absorbed
• In an endothermic reaction, the activation energy is typically lower than in exothermic reactions.

  False
• What is a reaction profile in chemistry?

  Graphical representation of energy changes
• Endothermic reactions require energy to be absorbed
• An exothermic reaction results in products with lower energy than the reactants.
• What is the energy level of the transition state?

  Highest
• In exothermic reactions, the activation energy is generally lower than in endothermic reactions.
• Match the term with its description:

  Activation energy ↔️ Peak height on reaction profile

  Enthalpy change ↔️ Difference in energy levels of reactants and products
• Match the reaction type with its energy change:

  Exothermic ↔️ Energy is released

  Endothermic ↔️ Energy is absorbed
• Exothermic reactions typically have lower activation energies than endothermic reactions.


  True
• Exothermic reactions release energy and have generally lower activation energies
• The transition state is a stable and long-lived intermediate during a reaction.

  False
• Match the key features of the transition state with their descriptions:

  Energy ↔️ Highest energy state

  Stability ↔️ Unstable

  Lifetime ↔️ Short-lived

  Bond Status ↔️ Bonds breaking and forming
• The enthalpy change in a reaction profile represents the overall energy change between the reactants and products.
• Why is the activation energy generally higher in endothermic reactions?

  Energy must be absorbed
• Match the features of a reaction profile with their descriptions:

  Reactants ↔️ Starting point with initial energy

  Products ↔️ End point with final energy

  Activation energy ↔️ Minimum energy to start reaction

  Enthalpy change ↔️ Overall energy change
• Understanding the reaction profile helps explain the energy changes involved in a chemical reaction.


  True
• Match the activation energy level with the reaction rate:

  Low ↔️ Fast

  High ↔️ Slow
• Endothermic reactions absorb energy, resulting in products with higher energy than the reactants.

  True
• A reaction profile shows how the energy of the system changes as the reaction progresses from reactants to products.


  True
• Why is activation energy higher in endothermic reactions?

  Energy is absorbed to form less stable products
• Activation energy is the energy required to initiate a chemical reaction.


  True
• The enthalpy change is the overall energy change between reactants and products
• Activation energy is the energy needed to break bonds in reactants and form the transition state
• The transition state represents the state where reactants have partially broken original bonds and are beginning to form new bonds
• The transition state occurs when reactants have fully formed new bonds.

  False
• Arrange the key features of a reaction profile in the order they appear during a reaction:

  1️⃣ Reactants

  2️⃣ Activation energy

  3️⃣ Products
• Exothermic reactions have a generally lower activation energy.
• What is a reaction profile used to illustrate?

  Energy changes in reactions
• The minimum energy required to start a chemical reaction is called activation energy.
• Lower activation energies lead to faster reaction rates.


  True
• The transition state has a short lifetime because it is highly unstable.
• In exothermic reactions, the products have a lower energy level than the reactants.

  True
• What does a positive enthalpy change indicate about a reaction?

  Endothermic reaction