5.2 Reaction profiles

• What is a reaction profile?

  A graph of energy changes
• What does a reaction profile plot against the progress of the reaction?

  Energy
• What does a reaction profile highlight about activation energy?

  Its importance in reactions
• A reaction profile helps visualize whether a reaction is exothermic or endothermic.
• An exothermic reaction releases energy and has a high activation energy.

  False
• What is activation energy in chemical reactions?

  The minimum energy required
• Activation energy is the minimum amount of energy required to start a chemical reaction
• Exothermic reactions have a low activation energy
• What is a reaction profile?

  Graph of energy changes
• Reactants in a reaction profile represent the starting materials of the chemical reaction.


  True
• For endothermic reactions, the activation energy is high and energy is absorbed.

  True
• The overall energy change in an exothermic reaction is negative.

  True
• Endothermic reactions release energy to the surroundings.

  False
• Order the properties of exothermic and endothermic reactions:

  1️⃣ Exothermic reactions release energy

  2️⃣ Exothermic reactions have low activation energy

  3️⃣ Endothermic reactions absorb energy

  4️⃣ Endothermic reactions have high activation energy
• Endothermic reactions require a significant energy input to start the reaction.


  True
• A reaction profile plots energy against the progress of the reaction.
• Activation energy is the minimum energy required to start a reaction
• Activation energy represents the energy barrier that reactants must overcome for a reaction to proceed.

  True
• Exothermic reactions have a low activation energy
• An example of an exothermic reaction is the combustion of methane
• Match the reaction type with its key features:

  Exothermic ↔️ Low activation energy

  Endothermic ↔️ High activation energy
• Reactants are always at a lower energy level than products.

  False
• What is the typical energy level of reactants compared to products?

  Higher
• What is the relationship between activation energy and reaction rate in endothermic reactions?

  Higher Ea, slower rate
• Exothermic reactions release energy into the environment


  True
• The minimum energy required to start a chemical reaction is called activation energy.
• What does the overall energy change in a reaction indicate?

  Whether energy is absorbed or released
• Match the feature of a reaction profile with its description:

  Reactants ↔️ Starting materials in the reaction

  Products ↔️ Substances formed at the end

  Activation energy ↔️ Minimum energy to start

  Energy change ↔️ Difference in energy
• Order the steps to describe a reaction profile:

  1️⃣ Define the reaction profile

  2️⃣ Identify reactants and products

  3️⃣ Describe activation energy

  4️⃣ Explain overall energy change
• Exothermic reactions release energy because they have a low activation energy.

  True
• What type of reactions have a high activation energy?

  Endothermic reactions
• Reactions with lower activation energies occur more spontaneously.


  True
• A reaction profile plots the energy of the system against the progress of the reaction
• The energy change in a reaction profile is the difference in energy between the reactants and products
• Order the energy changes in a reaction profile for an endothermic reaction:

  1️⃣ High activation energy

  2️⃣ Energy absorbed
• What feature in a reaction profile indicates the activation energy?

  Peak representing transition state
• What is the overall energy change in an endothermic reaction?

  Absorption of energy
• Exothermic reactions release energy
• Reactants typically have a higher energy level than products in an exothermic reaction.


  True
• Exothermic reactions have low activation energy and release energy.

  True