Draw the reaction-energy diagram for the following reverse reaction:
•CH₃ + HCl → CH₄ + Cl•

Verified step by step guidance

1. Step 1: Understand the reverse reaction. The reverse reaction involves the formation of a methyl radical (•CH3) and hydrogen chloride (HCl) from methane (CH4) and a chlorine radical (Cl•). This is the reverse of a typical radical halogenation reaction.
2. Step 2: Identify the energy components of the reaction. The reaction-energy diagram will include the reactants (CH4 and Cl•), the transition state, and the products (•CH3 and HCl). The energy of the transition state will be higher than both the reactants and products.
3. Step 3: Determine the relative energy levels. Methane (CH4) is a stable molecule, so it will have a lower energy compared to the methyl radical (•CH3). The chlorine radical (Cl•) is also relatively reactive, so its energy will be higher than CH4 but lower than the transition state.
4. Step 4: Sketch the reaction-energy diagram. On the y-axis, plot the energy levels, and on the x-axis, plot the reaction progress. Start with CH4 and Cl• as the reactants, show a peak for the transition state, and end with •CH3 and HCl as the products. Label each part of the diagram clearly.
5. Step 5: Indicate the activation energy and overall energy change. The activation energy is the difference between the energy of the reactants and the transition state. The overall energy change (ΔE) is the difference between the energy of the reactants and the products. Ensure these are marked on the diagram.

Key Concepts

Reaction Energy Diagram

A reaction energy diagram visually represents the energy changes during a chemical reaction. It typically includes the energy of reactants and products, as well as the activation energy required for the reaction to proceed. The diagram helps illustrate the transition state and the overall energy change, indicating whether the reaction is exothermic or endothermic.

Activation Energy

Activation energy is the minimum energy required for a chemical reaction to occur. It represents the energy barrier that reactants must overcome to form products. In a reaction energy diagram, this is depicted as the peak of the curve, where the transition state exists before the system can proceed to the products.

Bond Dissociation Energy

Bond dissociation energy is the energy required to break a specific bond in a molecule. In the context of the given reaction, understanding the bond dissociation energies of H-Cl and C-H bonds is crucial for predicting the energy changes during the reaction. This concept helps explain the stability of reactants and products and their relative energies in the reaction energy diagram.