Intermediate Topic 503 of 1102 Kinetics & Equilibrium
Reaction Coordinate Diagram
A graph showing energy changes along the reaction path with barriers and intermediates.
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In-depth explanation of Reaction Coordinate Diagram
A reaction coordinate diagram plots the energy of the system against reaction progress, showing the energy changes as the reaction proceeds along its lowest energy path. Reactants and products appear as valleys or minima, transition states appear as peaks, and intermediates appear as shallow valleys between peaks. The height of each peak relative to the preceding valley gives the activation energy of that step. The highest peak on the diagram generally corresponds to the rate-determining step, because it has the largest barrier and therefore the slowest rate. The vertical difference between reactants and products gives the overall energy change of the reaction.
Going deeper: Reaction Coordinate Diagram
Key ideas: Reading rules: Ea forward is peak minus reactant, Ea reverse is peak minus product, and delta H is product minus reactant. A catalyst lowers the peaks but leaves the reactant and product levels where they are. For a multistep reaction the rate-determining step is the highest transition state relative to the preceding intermediate, and the overall barrier is measured from the lowest preceding point.
Common mistakes and connections: Students label transition states as intermediates or measure Ea from the wrong baseline. Another mistake is to draw a catalysed path that changes the product energy. The x axis is not time, and the width of a peak carries no meaning. Also remember that an endothermic reaction has Ea forward greater than delta H. Ties together activation energy, mechanism, Hammond postulate and catalysis.
Visualization of Reaction Coordinate Diagram
Peaks are transition states, valleys are intermediates, and the highest peak marks the rate-determining step; the end levels give the overall energy change. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A two-step mechanism appears as two peaks with an intermediate valley between them, and the higher peak controls the rate.
Frequently asked questions about Reaction Coordinate Diagram
What is Reaction Coordinate Diagram?
A graph showing energy changes along the reaction path with barriers and intermediates.
Is Reaction Coordinate Diagram a beginner, intermediate or advanced topic?
Reaction Coordinate Diagram is a intermediate topic in Kinetics & Equilibrium. It builds on the vocabulary of beginner topics in this area.
What should I learn before Reaction Coordinate Diagram?
Study these earlier topics in Kinetics & Equilibrium first: Inhibitors and Poisons, Surface Catalysis Steps, Zeolites.
What comes after Reaction Coordinate Diagram?
The next topics in Kinetics & Equilibrium are Equilibrium in Biology and Buffer Equilibria.
Can I practise Reaction Coordinate Diagram with quizzes?
Yes. The interactive lesson includes a self-check question on Reaction Coordinate Diagram, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Reaction Coordinate Diagram fits in Kinetics & Equilibrium
Reaction Coordinate Diagram is topic 84 of 91 in Kinetics & Equilibrium.