Question Video: Interpreting a Reaction Profile Diagram Chemistry

In which of these reaction profile diagrams is the energy required to break chemical bonds the greatest? [A] Reaction profile diagram A [B] Reaction profile diagram B [C] Reaction profile diagram C [D] Reaction profile diagram D

02:41

Video Transcript

In which of these reaction profile diagrams is the energy required to break chemical bonds the greatest?

Reaction profile diagrams are graphs that represent the changes in the energies of substances during a reaction. The 𝑥-axis represents the progress of the reaction over time. And the 𝑦-axis represents the energies of the substances during the reaction. The graph contains three main parts. The first flat segment on the left represents the reactants. The peak of the graph represents the transition state. And the flat section on the right represents the products. In order for a chemical reaction to occur, enough energy must be absorbed to bring the reactants to the transition state. This energy is called activation energy. It’s the amount of energy needed to break bonds and begin to rearrange atoms so product molecules can form.

We can determine activation energy from the graph by finding the difference between the energy of the transition state and the energy of the reactants. During the transition state, reactant molecules have just the right amount of energy and the correct orientation in space for product molecules to begin to form. As new bonds form in the product molecules, energy is released. Finally, the difference between the reactants and products’ energy is the enthalpy of the reaction, or Δ𝐻. However, we are not going to focus on enthalpy in this video.

In this question, we are asked to identify the reaction profile diagram in which the energy required to break chemical bonds is the greatest. The energy needed to break the chemical bonds is the activation energy. Let’s find the activation energy on each of the reaction profile diagrams in the answer choices. The bottom-left segment of each reaction profile represents the energy of the reactants. And the peak or maximum point of each reaction profile represents the transition state. The vertical distance between these two points on the graph is the activation energy.

In choice (A), the difference between the transition state and reactants’ energy is the greatest, which means that the energy required to break chemical bonds is also the greatest. The correct answer is choice (A).

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.