Draw an energy diagram for a two-step exergonic reaction whose second step is faster than its fi

Draw an energy diagram for a two-step exergonic reaction...

Key Concepts

Energy Diagram

An energy diagram (or reaction coordinate diagram) is a graphical depiction of the changes in free energy during a chemical reaction. It illustrates the energy profile from the reactants through intermediate states and transition states to the final products, making it easier to understand the energetics and kinetics of each reaction step.

Exergonic Reaction

An exergonic reaction is characterized by a negative overall change in Gibbs free energy, meaning that the reaction releases energy. In an energy diagram, this is depicted by the products having a lower energy level than the reactants, indicating that the reaction proceeds spontaneously under standard conditions.

Multi-step Reaction and Rate-Determining Step

In multi-step reactions, the overall process is divided into distinct steps, each potentially with its own energy barrier. The rate-determining step is the slowest step in the sequence and governs the overall reaction rate. In a two-step reaction where the second step is faster, the first step (with a higher activation energy) is the rate-determining step.

Transition State and Activation Energy

Each step in a reaction has an associated transition state, which is a high-energy, unstable configuration that the reaction must pass through. The energy difference between the reactants (or intermediate) and the transition state is known as the activation energy. This concept is critical to understanding why one step may be slower (having a higher activation energy) than another.

Transcript

00:01 In this question, we are going to draw the energy diagram for a two -step reaction, where the second step of the reaction is faster than the first step of the reaction.

00:11 So now let's recall the definition of gibbs free energy change.

00:19 And that is the difference between the free energy of the products minus the free energy of the reactants.

00:36 So if the gips free energy change is negative, then the free energy of the products is less than the free energy of the reactants.

01:34 Therefore, the reaction is exogonic, and that means that the forward reaction is.

01:54 Energetically favorable and the reaction occurs spontaneously since it occurs with the release of heat.

02:12 Okay? also, seeing that it is a two -step reaction where the first step is slower than the second.

02:27 So we have a two -step reaction, right? so if the second step is faster, that means that that the activation energy of the second step is less than the activation energy of the first step.

03:20 Okay, so now let's represent that in an energy diagram.

03:30 Okay, so we have two steps that we need to account for.

03:36 So now let's just start off with the reactants.

03:54 Now let's draw the first step of reaction.

04:05 Okay, so the highest energy structure of the reaction.

04:08 Reaction would be the transition state...

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