Question

Consider the following energy diagram

1. How many steps are involved in this reaction?
2. Label $\mathbf{∆}{\mathbf{H}}^{\mathbf{°}}$and ${\mathbf{E}}_{\mathbf{a}}$ for each step, and label$\mathbf{∆}{{\mathbf{H}}^{\mathbf{°}}}_{\mathbf{overall}}$ .
3. Label each transition state.
4. Which point on the graph corresponds to a reactive intermediate?
5. Which step is rate-determining?
6. Is the overall reaction endothermic or exothermic?

Short answer

Answer

1. The reaction involves two steps.
2. Labeled in the given energy diagram.
3. Labeled in the given energy diagram.
4. The dip/valley corresponds to a reactive intermediate.
5. The first step is the rate-determining step.
6. The overall reaction is endothermic.

Step-by-step solution

Step-by-Step SolutionStep 1: Energy diagram of a reaction

The energy changes occurring during a chemical reaction are represented using the plot of reaction coordinate vs. energy.

In an energy diagram, the peaks represent the transition states, and the valleys represent the reactive intermediates.

The energy difference between the reactants and the transition state is referred to as the activation energy.

Enthalpy of a reaction

Endothermic reactions have a positive $∆{\mathrm{H}}^{°}$, while exothermic reactions have a negative $∆{\mathrm{H}}^{°}$.

Energy plot of a reaction

The given energy diagram represents the various parameters involved in a chemical reaction.

Energy diagram

The reaction involves two steps indicated using two energy barriers.

The rate-determining steps are the steps in which the conversion of reactants to products happens very slowly (i.e., the ones that have higher activation energy).

In this case, the first step is the rate-determining step.

The overall reaction is endothermic as the products are in higher energy than the reactants. Hence $∆{\mathrm{H}}^{°}$ is positive.