Question

The following reaction is exothermic: $$ 2 \mathrm{O}_{3}(g) \longrightarrow 3 \mathrm{O}_{2}(g) $$ Draw an energy diagram that shows the relative energies of the reactants, products, and the activated complex. Label the diagram with molecular representations of reactants, products, and a possible structure for the activated complex.

Short answer

The completed energy diagram would exhibit a peak, depicting the activated complex, that is higher than the reactants and products. The line representing the reactants (\(O_{3}\)) will be higher than the line representing the products (\(O_{2}\)), which shows that the energy of the products is lower than that of the reactants, hence depicting an exothermic reaction.

Step-by-step solution

Identifying the Reactants and Products

The reactants and products are given in the chemical reaction: \(2 \mathrm{O}_{3}(g) \longrightarrow 3 \mathrm{O}_{2}(g)\). Hence, it's seen that the reactants are ozone molecules (\(O_{3}\)) and the products are oxygen molecules (\(O_{2}\)).

Establish the energy levels of reactants and products

In this exothermic reaction, the products have less energy than the reactants. Therefore, in the energy diagram, the position for the \(O_{2}\) molecules is lower than for the \(O_{3}\) molecules.

Consider the Activated Complex

The activated complex, also called transition state, is the state corresponding to the highest potential energy along the reaction path. The activated complex of the reaction is typically higher in energy than either the reactants or products.

Adjoin Labels

Label the energy graph with molecular representations of reactants, products, and the possible structure for the activated complex. The y-axis represents energy, while the x-axis represents the progress of the reaction.

Drawing the Energy Diagram

Draw a spike or a peak on the diagram to represent the activated complex, which should be higher than the reactants and products. The line starts at the energy level of the reactants, ascends to the energy level of the activated complex (peak), and then descends to the energy level of the products.

Key concepts

Exothermic Reaction

An exothermic reaction is a chemical reaction that releases energy to the surroundings, typically in the form of heat, light, or sound. This process results in the products having less energy than the reactants.

In simpler terms, an exothermic reaction is like a firework exploding. It starts with storing energy and once ignited, releases this energy into the environment.

In the case of the reaction involving ozone (\(2 \mathrm{O}_{3}(g) \longrightarrow 3 \mathrm{O}_{2}(g)\)), energy is released as the chemical bonds in the ozone (\(O_{3}\)) break and form new bonds to create oxygen molecules (\(O_{2}\)), which are more stable and lower in energy.

On an energy diagram, you will notice:

• The reactants \(O_{3}\) at a higher energy than the products \(O_{2}\).
• A downward slope indicating that energy is emitted.

Activated Complex

In a chemical reaction, the activated complex is a temporary, unstable state that occurs when reactants form an intermediate or "transition" state before creating the final products. This state is sometimes referred to as the transition state.

Picture a mountain path: the activated complex is the highest point on this path, representing a barrier that must be overcome for the reaction to proceed.

In the energy diagram, this is represented by a peak between the energy levels of the reactants and products.

Here’s a simplified breakdown:

• The reactants start by climbing up to the peak, using energy for this transition.
• At the peak, you have the activated complex where potential energy is at its maximum.
• Once the top is reached, the reactants convert into products as the system releases energy, moving downhill.

Thus, understanding the activated complex is crucial as it indicates the moment when bonds are broken and new ones are formed.

Molecular Representations

Molecular representations are a way to visualize atoms, bonds, and molecules involved in a reaction, helping chemists understand and communicate complex chemical processes effectively.

For the reaction \(2 \mathrm{O}_{3}(g) \rightarrow 3 \mathrm{O}_{2}(g)\), we can use molecular representations to see:

• Each \(O_{3}\) molecule depicted as three oxygen atoms bonded, forming a bent shape.
• The transition to \(O_{2}\), shown as pairs of oxygen atoms doubly bonded, representing diatomic oxygen.
• The potential structure of the activated complex, possibly showing a partially formed set of bonds halfway through the transition from \(O_{3}\) to \(O_{2}\).

By integrating these visual models on an energy diagram, learners get a clearer view of how molecules transform during a reaction progress, enhancing comprehension.