Sketch an energy diagram for a two-step reaction in which both steps are exergonic and in which

Sketch an energy diagram for a two-step reaction in which...

Key Concepts

Overall ?G (Gibbs Free Energy Change)

The overall ?G is the net change in free energy between the reactants and the products for the entire reaction. In an exergonic reaction, this value is negative, reflecting that the products are more stable (lower in energy) than the reactants.

Energy Diagram

An energy diagram is a graphical representation of the changes in energy during a chemical reaction. It shows the relative energy of reactants, products, transition states, and intermediates along the reaction coordinate, enabling visualization of the energy barriers that must be overcome during the reaction.

Exergonic Reaction

An exergonic reaction is one in which the overall change in free energy (?G°) is negative, indicating that the reaction releases energy. This concept is fundamental to understanding reaction spontaneity and the direction in which a reaction will proceed.

Transition State

The transition state is a high-energy, unstable configuration of atoms at the peak of the energy barrier between reactants and products. It represents the point of maximum energy along the reaction pathway, and its energy level determines the activation energy (?G‡) required for the reaction to occur.

Intermediate

In a multistep reaction, an intermediate is a transient species that appears between the initial reactant and the final product. On an energy diagram, an intermediate is depicted as a local minimum, representing its lower energy relative to the transition states of the steps that form and consume it.

Activation Energy (?G‡)

Activation energy is the amount of energy needed for a reaction to reach the transition state from the reactants, serving as a kinetic barrier to the reaction. Each step in a multistep reaction has its own activation energy, which is depicted as the energy difference between the reactant (or intermediate) and the corresponding transition state.

Transcript

00:01 So in this question, we're asked to sketch the energy diagram for a two -step reaction.

00:08 And so there's a few steps that are guidelines that we need to follow when we're drawing this diagram.

00:15 So both steps are exergonic, which means that in both steps, energy is going to be released.

00:21 And the second step has a greater transition state than the first step.

00:24 And lastly, we need to label the reactant, the product, and the intermediate, as well as the overall activation energy.

00:31 And the overall gives free energy.

00:34 So let's begin by first drawing the diagram.

00:39 So we're going to have a graph here.

00:41 And so the graph is going to represent the progress of the reaction on one side.

00:53 And then on the y -axis, it's going to represent the energy.

01:00 So we know that it's a two -step reaction.

01:04 So there's going to be, and each step is exergonic, which means energy is going to be released.

01:09 So the amount of energy that the reaction starts with is going to be greater than the amount of energy that the reaction ends with.

01:16 So say we start here and then the reaction is going to have, let me start over.

01:23 So if we start here, the reaction is going to stop here, then it's going to start off here.

01:29 And then the second step has a greater transition energy than the first step or transition state.

01:34 So the peak is going to be higher because the transition state is where the reaction is at its highest.

01:41 Energy level.

01:42 So in the first reaction, the transition state is here, but the second transition state has a higher transition, the second reaction has a higher transition state.

01:53 So its energy is going to be greater.

01:56 And then since it's going to be releasing energy, the overall reaction is going to look like that.

02:02 So we're going to get a graph that looks something like this.

02:07 And then now we need to make sure that we've fulfilled all of the guidelines.

02:12 So it's exergonic.

02:13 And the reason why we know it's extradonic is because this is where the reactant is.

02:18 So i can label this the reactive.

02:26 And this is going to be the product...